The length of a rectangle is 3 inches more than its width if the perimeter is 42 in find the dimensions of the rectangle

The problem uses the perimeter formula. P = 2w + 2l where w is the width, and l is the length.

We know the length (l) is 3 inches longer than it's width (or l = w+3). Substitute w + 3 into Perimeter equation.

P = 2w + 2 (w+3). That simplifies to P = 4w + 6.

Since P + 42, we have 42 = 4w + 6.

With some simple algebra we find that w = 9 and l = 12.