Answer: w = 4 or w = 0
Explanation:
The greatest common factor is 10w, so you can factor that out to get
10w(w-4) = 0
One or both of the factors being multiplied (10w and w-4) must equal zero for their product to equal zero.
Set both of the factors equal to zero and solve the separate equations:
10w = 0
w = 0
w - 4 = 0
w = 4
w = 4 or w = 0