Question

What is the value of x in the solution to this system of equations?

4x+7y=85

x=2y−5

A. x = -9
B. x = 9
C. x = 8
D. x = 3

Answer 1

B

Explanation:

I used substitution to solve this system. I'll run through all of my steps below:

`4x+7y=85\\x=2y-5`

I'm going to replace the 'x' values in the first equation with the entire second equation.

`4(2y-5)+7y=85`

`8y-20+7y=85\\15y-20=85\\15y=105\\y=7`

Now that we know what y equals, we can go back and solve for x.

`x=2(7)-5\\x=14-5\\x=9`

Hope this helps!