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.
