Answer:
1. 9x
2. 13xy
3. 12m
4. 5mn
5. -8xyz
The variables in each item are all the same. You can add the equation directly.
Dont be confused of having a negative sign. For example, item number 3. 15m + -3m= you can change the operation into subtraction form resulting to this 15m - 3m= 12m.
REMEMBER: POSITIVE SIGN PLUS POSITIVE SIGN IS EQUAL TO POSITVE SIGN (+ + += +)
NEGATIVE SIGN PLUS NEGATIVE SIGN IS EQUAL TO POSTIVE SIGN (- + -= +)
POSITIVE SIGN PLUS NEGATIVE SIGN IS EQUAL TO NEGATIVE SIGN (+ + -= -)
