Finding the value of w
We want to find the value of w that makes m = 8 in the equation:
m = w - 4
We just replace m by 8 in the equation:
m = w - 4
8 = w - 4
We add 4 both sides of the equation:
8 + 4 = w - 4 + 4
8 + 4 = w
12 = w
Then
if w = 12, then m = 8