They want you to do two different problems: 1) add the two together, and then 2) subtract the larger value from the smaller. That's why they want you to compare the numbers first to figure out the larger number (i.e. They don't want you to subtract the smaller number from the larger number): 8/9 + 1/4 = 41/36 8/9 - 1/4 = 27/36 or 3/13