Use mental math to figure out
1. 28+ 65.

2. 14+ 6+ 57

3. 80 + 40 + 170

4. 432 +250

5. 82 - 37

6. 1245 - 320

7. 532 - 116

the solution is 12x-6y

you could deduce the conclusion directly using the facts pertaining to the specific situation.

hope this .