I think this attachment will help you
width = 10 feet → C
let l represent the length then width = l - 8
perimeter = 2(length + width) = 2(l + l - 8)
given perimeter = 56 then
2(2l - 8)= 56
divide both sides by 2
2l - 8 = = 28
add 8 to both sides
2l = 28 + 8 = 36
divide both sides by 2
l = = 18
thus length = 18 feet and width = 18 - 8 = 10 feet
A because there is a difference between a expression and equation. Expressions don’t have a equal sign or an answer. But equations have an equal sign and an answer. So because everything else has an answer or equal sign, the correct answer would be A. Hope this helps!