The formula of a perimeter of rectangle:
P = 2(w + l)
We have l = 12 in and P = 56 in.
Substitute:
2(w + 12) = 56 use distributive property
(2)(w) + (2)(12) = 56
2w + 24 = 56 subtract 24 from both sides
2w = 32 divide both sides by 2
w = 16
Answer: D. 16 in.
