What is the answer?

Hi guest answerer.

If you take very cold air out of a room then the room becomes warmer doesn't it ?

If it becomes warmer then the temperature goes up.

The very  cold air was a negative temperature.

So this is one explanation of why  taking away the negative number is the same as adding the positive version of it.

6 - - 3 = 6 + 3 = 9

so for the original question.

5 - x = 12

the only way this can happen is if x is a negative number.    We know that

5 + 7 = 12

so

5 - - 7 = 12

x must be -7

x=17          but it is incorrect        5-anything cannot =12   only x-5=12