Sarah Needs to Solve This Word Problem: a Sweater in a Store

Multiple Choice

Sarah needs to solve this word problem: A sweater in a store is originally priced at $40, but the price tag is marked "One-half off." The sweater is placed on a rack marked "Five dollars off the sale price." How much does the sweater cost now?
Sarah knows how to find one-half of a number; she also knows how to subtract one number from another. She uses both of these operations to arrive at the correct answer of $15. Which one of the following best describes Sarah's approach to problem solving?

A) Drawing an analogy
B) Availability
C) Working backward
D) Combining algorithms