Question

How do i use substitution to solve each system?

y= 0.8x + 7.2
20x + 32y=48

Answer 1

I would rearrange them to know what I had.
0.8x - y = -7.2
20x +32y = 48

Then I would consider taking out the largest factor I could in the second equation. That would be a factor of 4.

For solving by substitution, I would solve the first equation for y which would be -y = -7.2 - 0.8x or
y = 7.2+0.8x

Substitute this value for y into the second equation and go from there.

Answer 2

your first equation tells you what y is, so sub that into the second

20x + 32(.8x+7.2) = 48

solve for x, then sub that x value back into the first equation to get y.