Algebra (check answers)
posted by Stacie on .
Could you please check my answers we are using substitution to solve each system of equations. And at the end of every solution you are supposed to have an answer as a coordinate.
1. x=2y
x+y=3
Answer (1,2)
2. 2y=3
xy=10
Answer: (10,10)
3. y=x+7
x+2y= 21
Answer: (3,4)
4. 2y=x
xy=10
Answer: (6,1)
5. x+y=0
4x+4y=0
Answer: (0,0)
6. 2xy=6
3x5y=9
Answer: (3,0)
7. 4xy= 6
y+2=x
Answer: (8,30)
8. 4xy= 3
Answer: (3,6)
9. x5y=11
3x+y=7
Answer: infinitely many
10. x2y=5
3x5y=8
Answer: (1.75, 8.5)
11. Laura and Ji Yong were jogging on a 10 mile path. Laura had a 2mile head start on Ju Yong. If Laura ran at an average rate of 5 miles per hour and JiYong ran at an average rate of 8 miles per hour, how long would it take for JiYong to catch up with Laura.
Answer: 4 miles.

none of your equation answers are correct.
I will #3 for you then follow the same method to do the rest
3. y=x+7
x+2y= 21
sub the first into the second:
x + 2(x+7) = 21
x + 2x + 14 = 21
3x = 35
x = 35/3
now sub that back into the first
y = 35/3 + 7 = 35/3 + 21/3 = 14/3
check:
in #1
LS = y = 14/3
RS = x+7 = 35/3 + 7 = 14/3
in #2
LS = x+2y = 35/3 + 2(14/3) = 21
RS = 21
now work each one out the same way, and check your answer the same way. 
If you know how to do this substitution let me know but if you don't that's okay. Also, the last one I redid I got 52:30

x2y=1 x+5y=4 x=1 y=1