Question

The area of a rectangle is 70 in² and the length of the rectangle is 3 in. longer than the width.

Answer 1

First, let's start out with the formula for the area of a rectangle.
A = w × l

Define the variables:
A = area
w = width
l = length

So here, the area is 70 in².
70 = w × l

The length is 3 in. longer than the width.
l = w + 3

Now all that's left is plugging the l in.
70 = w × (w + 3)

This can also look like:
w(w+3) = 70