## Algebra 1: Common Core (15th Edition)

The width of Ben's rectangular family room is 3 ft less than the length. $w=l-3$ The perimeter is 70 ft: $P=2(l+w)=70$ Using substitution: $2(l+w)=70$ $2(l+l-3)=70$ $2(2l-3)=70$ Hence, the correct answer is I.