Consider the question. Betty is saving money for a new wallet which costs $100. Betty has only half of the money she needs. Her parents decided to give her $15 for that purpose, and her grandparents twice as much as her parents. How much more money does Betty need to buy the wallet?
 What is the step-by-step reasoning process to arrive at the answer: 5?
In the beginning, Betty has only 100 / 2 = $50. Betty's grandparents gave her 15 * 2 = $30. This means, Betty needs 100 - 50 - 30 - 15 = $5 more.