You have the following equation:
5x - 3y = -45
In order to solve the previous equation for y, you proceed as follow:
5x - 3y = -45 subtract 5x both sides
- 3y = -45 - 5x multiply by -1 both sides
(-1)(-3y) = (-1)(-45 - 5x)
3y = 45 + 5x divide by 3 both sides
y = 45/3 + 5/3 x order the right side
y = 5/3 x + 15
Hence, the solution for y is y = 5/3 x + 15