I'll just do 2 of them.
Remember that a positive minus a negative number is basically the positive plus positive. Example: 1-(-1) is equal to 1+1. The same goes for a positive plus a negative. Example: 1+(-1) = 1-1
For #4, we see 7-11. Using the rule, we can see that we can change this to 7+(-11).
For #11, the equation is -34-(-15)-(-18) so we can change this to:
-34+15+18. Always use the rule above!
