so the way you would do this problem would be to solve for how many pens he was able to buy if he bought $9.75 worth of pens for $0.75 each. so to find the number of pens you would do 9.75/0.75, which equals a total of 13 pens. so he bought 4 times as many pencils so to find the number of pencils he purchased you would multiply 13 by 4 which equals 52 total pencils. to find the cost that aaron paid total you would multiply 52x0.35 which equals $18.20