So, this is simple, but needed to be one step at a time. We need to find out how much she earns by washing one window, and to do that we need to divide $81 by 9, and after that division she earns $9 per window. If she washes 5 windows, multiply $9 by 5 as that's how much she's going to earn. So, when she washes 5 windows, she earns $45.
