Question

the length is 3 more inches than the width the perimeter is 30 inches

Answer 1

length is 9 inches and the width is 6 inches lol did that in my head

Answer 2

so I'm guessing this is a rectangle? =)
if so
P=l+l+w+w
or P=2l+2w
l=3+w
P=30

Answer 3

30=2l+2w
30=2(3+w)+2w
30=6+2w+2w
30=6+4w
24=4w
6=w

Answer 4

l=3+w
l=3+6
l=9