Question 786885
length = 6w
P = 2l + 2w
126 = 2(6w) + 2w
126 = 12w + 2w
126 = 14w
126/14 = w
9 = w

check:
126 + 2(6(9)) + 2(9)
126 = 108 + 18
126 = 126