Problem 23: I think of a number, divide it by 2 then add 12. If the answer is 20, what was the original number?

Predict: I predict that I will need to use subtraction in this problem.

Clarify: I have no words, sentences or phrases to clarify.

Find the big question: What was the original number?

Solve:

- Since I have to reverse the process, because I have to find the original number, we will reverse the operations too.
- The equation that they did was: __ / 2 + 12 = 20. But since we are reversing it we are doing subtraction and multiplication, because they are the opposite operation.
- The equation that w are doing is: 20 – 12 x 2 = 16.

The answer is 16.

Summary: The mathematicians toolbox strategy that I used in this sum was work backwards.