75÷500 = 0.15 multiply with a hundred to get percentage equals 15℅
2x+3x+2=-4(cause y=3x+2)
5x=-6
x=-6/5
f(-6/5)=-8/5
negative 6 over 5
There is actually 2 ways to solve this, I will show you both.
The first is obvious, solve for x in the first one, and plug it into the 2nd one and get the answer
4x + 7 = 12
4x = 5
x = 
8(
) + 3
2 * 5 + 3
10 + 3
13
The 2nd option is to manipulate the 4x + 7 to be 8x + 3
4x + 7 = 12
start by moving the 7 over
4x = 5
multiply both sides by 2
8x = 10
and add 3 to both sides
8x + 3 = 13