This is a classic example of where you would need to use the process of elimination. Let's start with answer A, 3 classes. If A were to be correct, 3 classes of 45 minutes each would be 132 greater than the amount he paid, 3 classes worth $12. We could easily express this as a math equation:
45 * 3 = 132 + (12 * 3) Then, all you would have to do is simplify: 135 = 132 + 36 135 = 168
Obviously this equation isn't true, and you can continue with answer choice B. But wait... there's a better way. Using this starting equation, we can come up with a formula to solve for c, the number of classes. Let's take our starting equation:
45 * 3 = 132 + (12 * 3) Now, let's turn all the 3s into cs. 45c = 132 + 12c Then, using algebra, we can solve this equation. -12c - 12c 33c = 132 33c/33 = 132/33 c = 4
And finally, we have our answer, B! I hope both methods help you in your further studies.
