This will include all of the factors that can be multiplied together to total 72 because area of a rectangle is L x W.
1 x 72 = 72 1 and 72 are factors
2 x 36 = 72 2 and 36
3 x ? = 72.....
Include all of the numbers that you can find that equal 72 when multiplied together. These will fulfill the formula L x W which is area of a rectangle.