The simplified answer is 
If you are dividing powers with like terms you subtract the denominator to the numerator.
X + 4y = 3 x = -4y + 3
2x - 3y = 17
2(-4y + 3) - 3y = 17
-8y + 6 - 3y = 17
-11y + 6 = 17
-11y = 11
y = -1
x = -4(-1) + 3
x = 4 + 3
x = 7
(7, -1) is your answer
That has to be impossible because you can’t get any solution that would possible add to 6
I think 2(2x+20) would work.
there are other ones like: 4(x+10)
So with the problem the equation for answering these would be “1.50t+4=c” so to plug in the variable for t would be 0, 1, 2, 3, etc. and the variable c would be the answer of solving the equation with the plugged in number
1.50(0)+4= $4.00
1.50(1)+4= $5.50
1.50(2)+4= $7.00
1.50(3)+4= $8.50