Math(Please check answers)
posted by Hannah .
1) Solve the equation: 15(7x6) = 3x5
My answer is (85/108)
2) Mary and her brother collect coins. Mary has 4 times the number of coins that her brother has. Together they have 175 coins. How many does Mary have?
My answer is 140
3) Perform the indicated operations. Express the answer as a single polynomial in standard form.
(x1)(x^2 + 2x 3)
My answer is x^3 + x^2  5x + 3
4) Determine which values must be excluded from the domain.
x / x^2  9
My answer is x=3 and x=3
5) Solve the equation. The letters a,b,c are constants.
axb=c; a is not equal to 0.
My answer is x=b + c / a
6) Find c in the following.
For 4x^2  12x + c to be a perfect square, c must be?
The choices are 9 , 3 ,9, 0, or noe of the above.
My answer is none of the above.
7) Write the statment using symbols.
The sum of four and x is the product of 5 and y.
My answer is 4+x = 5y
8) write the number as a decimal.
3.875 x 10^9
My answer is 0.000000003875
Are these answers correct?

all ok, except #5 and #6
in #5 write it as (b+c)/a or else only b is divided by a
#6 should be 9 so that
4x^2 + 12 + 9 = (2x+3)^2 
Thank you!

(x2)(x+2)
___________
2(x3) 
I need to see the work for the problem 2/5x2875....I know the answer is 1725...but i need to see the process in order to answer the other questions.