To start, you need to get the total area of each individual roll of wrapping paper. To do this, you need to multiply the length x width, which would be 18 x 24 = 432. Then, you have three rolls so you mutiply that by three, which is 432 x 3 = 1296. You add the unit, and that leaves you with 1296 sq inches.
When dividing rational numbers, multiply by the "right" reciprocal. In this case, the "right" reciprocal means to take the reciprocal of the fraction on the right-hand side of the division operator.
