So I need help for a Math exam, this is one of the equations

If you have 5 potato chips, and I give you negative one potato chip, how many potato chips do you have? I know that it is impossible in real life, but just imagine how many potato chips you would have if I gave you negative one? That would make you have 4 potato chips.

 

5 potato chips plus negative 1 potato chips = 4 potato chips

5 + - 1

= 5 - 1

= 4

 

So...

   70 + - 60

= 70 - 60

= 10