6th grade math
posted by Alex .
Can you check my homework, please?
1. Write numeric expression for "eighteen less than the product of 2 and a".
Ans: 2a  8
2. Molly has x pieces of candy. Holly has twice as much. Write an expression to represent how much candy Holly has.
Ans: 2x
3. Jill wrote 6 letters to friends each month for n months. Write an expression to show the total number of letters Jill wrote.
Ans: 6n
4. Mary's sister is 6 years less than twice Mary's age. Mary is x years old. Write an expression to show her sister's age.
Ans: 2x  6
5. Evaluate: x^2 + (155+x) if x =3
Ans: 3^2 + (155+3)
= 3^2 + (10+3)
= 3^2 + 13
= 9+13
=22
6. Write an expression to show Joe's age when Sally is A years old.
Sally Joe
10 5
11 6
12 7
A ????
Ans: A  5
7. Write the expression for: 5 less than 8 times x
Ans: 8x  5
8. Evaluate: 3x+2xx+2+3+12
Ans: 4x + 17
9. At a costume party, there were 4 times as many superheroes as there were vampires. There were 10 pirates as well. Write an expression to represent how many superheroes, vampires, and pirates were at the party.
v = vampires
Ans: 4v + v + 10
= 5v + 10
10. Create an expression for the number 24. Use at least two operations in each expression.
Ans: (10x2) + (2x2) ???
11. Downloading music costs $0.89 per song, plus a registration fee of $15. Write an expression to represent the total cost to download x songs?
Ans: x($.89) + $15
12. At Saturday's basketball game, there were 20 more than half the fans at Friday's game. Assuming there were "x" fans at Friday's game, write an expression to represent the number of fans at Saturday's game?
Ans: (x/2) + 20
13. At DMS the students had a texting contest. One person will contact 2 people, and each of those people will contact 2 other people, and so on. How many people will be contacted in the fourth round? Write your answer in exponent form and find the value.
Ans: 2^8 = 40? not sure how to do it. can you explain and show the steps
14. In the Book Club, each student will get 4 new books. There is one group of 9 students and one group of 23 students. The expression 4 × (9 + 23) gives the total number of new books. Write the equivalent word expression.
Ans: 4 times 9 + 23 ?
15. Sue ordered 4 pizzas for 6 dollars each and 2 twelve packs of coke for x amount. Use the distributive property to create an equivalent expression.
Ans: not sure
16. Horace is 4 years younger than Kim. Jack is twice as old has Horace. Using k for Kim’s age, write an expression to represent Jack’s age?
Ans: 2(k4)
17. Mrs. Joyner’s math class is planning a trip to the zoo. It will cost $12 for the school bus and the price of a ticket is $15 per student. What value varies in this example?
Ans: number of students?
18. One person in my class will call 3 people, and each of those people will contact 3 other people, and so on. How many people will be contacted in the 5th round? Write your answer in exponent form and find the value.
Ans: similar to # 13, but don't know how to work it.
19. At the Braves game on Saturday, there were 50 more than half the fans at Friday's game. Assuming there were "x" fans at Friday's game, write an expression to represent the number of fans at Saturday's game?
Ans: (x/2) + 50

#1. I'd say 2a18
May be just a typo, but it will miss the mark on a test.
#13. After each round, double the number of existing people are added, giving 3 times the previous as a total:
Rnd Total
0 1
1 1+2 = 3
2 3+6 = 9
3 9+18 = 27
...
n 3^n
So, on the 4th round, 2*27 = 54 people were added.
And besides, 2^8 = 256, not 40!
#14. I'd say
four times the sum of nine and twentythree
#15. 4*6 + 2x
2(12+x)
#18. Try it now, using the method of #13.
The rest look good. 
1. It's actually 2a  18
2. Yep
3. Yep
4. Yep
5. Yep
6. Yep
7. Yep
8. Yep
9. Yep
10. I guess it's okay
11. Yep
12. Yep
13. 2^4 = 16 ; (the base 2 stands for the 2 people and 4 is the number of rounds)
14. Hmmm, "four multiplied by the sum of nine and twentythree"
15. 4(6) + 2(12)x ... though I'm not sure either :p
16. Yep
17. The total cost, because it depends on the number of students
18. 3^5 = 243
19. Yep
Hope this helps :3 
Thanks!
18. One person in my class will call 3 people, and each of those people will contact 3 other people, and so on. How many people will be contacted in the 5th round? Write your answer in exponent form and find the value.
Ans: 3^5 = 243
Still don't understand #15 though. Can you explain?