Can some one ! i really don't understand and plz explain

Length = l
width = 1/3 of length = l/3

perimeter = 2(l + l/3)
Answer is option B


2(l+ l/3) = 56
⇒ 8l/3 = 56
⇒ l = 3*56/8
⇒ l = 21 inch
width = 21/3 = 7inch

Area = 21*7 inch² = 147 inch²

Ibelieve it's a. 2.2 - x = -10.85 (plz tell me if it's right : ) )