What we know:
Width = w
Length = 4w + 6
Area = 130 in2
Area = W X L = 130
So, w X (4w + 6) = 130
4w2 + 6w = 130 by distributing
-130 -130
4w2 + 6w - 130 = 0
You can solve using the quadratic formula and by rejecting any negative lengths.