1) - 5/12 + ( - 13/18 ) = - 5/12 - 13/18 = - 15/36 - 26/36 = - 41/36 = - 5/36.

2)  3/10 + ( - 8/15 ) = 9/30 - 16/30 = - 7/30.

3)  - 1/6 - 7/18 = - 3/18 - 7/18 = - 10/18 = - 5/9.

4)  - 1/5 - ( - 7/15 ) = - 1/5 + 7/15 = - 3/15 + 7/15 = 4/15.