The given equation is:
P = 2w + 2l
We are given that:
P = 38
l = 12
Substitute with these two givens in the above equation to get the value of w which is the only unknown as follows:
P = 2w + 2l
38 = 2w + 2(12)
38 = 2w + 24
38 - 24 = 2w
2w = 14
w = 14/2 = 7