EXPLANATION
Given the equations:
1. P = 2L + 2W for W. (Subtracting 2L to both sides)
P - 2L = 2l + 2W - 2l (Dividing both sides by 2)
P/2 -2L/2 = W (Simplifying and switching)
W = P/2 - L
2. 2x + 3y = -10 for y. (Subtracting 2x to both sides)
2x - 2x + 3y = -10 -2x (Simplifying)
3y = -2x - 10 (Dividing both sides by 3)
y = -2x/3 - 10/3
