Consider the question. Sabrina gave 10 cookies to her brother. Her mother gave Sabrina half the number of cookies she gave her brother. Then Sabrina gave two-thirds of her cookies to her sister. If Sabrina had 20 cookies at the start, how many cookies are left with her?
 What is the step-by-step reasoning process to arrive at the answer: 5?
Sabrina had 20 - 10 = 10 cookies left after giving 10 cookies to her brother. Sabrina's mother gave her 10 / 2 = 5 cookies. So, she had 10 + 5 = 15 cookies then. She gave 15 x 2 / 3 = 10 cookies to her sister. Therefore, she only has 15 - 10 = 5 cookies left.