So the equation you would make is 63 / 9 = width
This is because the formula of finding the area of a rectangle is l x w = a.
So since we already know the length and area, we just plug them in and switch up the formula to find the width.
If 9 (length) x ? (width) = 63 (area), then 63 / 9 = ? (width)
If you calculate it in your mind or even a calculator, you will find that 63 / 9 = 7.
Therefore the width of the rectangle is 7.