In class we have been learning about adding and subtracting integers. The rules are:

•  if the signs are the same you add and move to the right of the number line
•  if the signs are different you subtract and move to the left of the number line

Eg. 5 + -7 = -2  (The signs in the middle are different so we subtract 7 from 5).
Eg. -8 - -7 = -1  (The signs in the middle are same so we add 7 onto -8).

by Jonty Stirling