Question

Add the following forces: 20 Newtons south, 30 newtons north, 40 newtons east, and 50 newtons west

Answer 1

The north and south forces have no effect on the east and west forces.
We can handle the two groups separately.

                       (20N south)  +  (30N north)

                   =  (20N south)  +  (20N north + 10N north)

                   =                              10N north .


                       (40N east)  +  (50N west)

                   =  (40N east)  +  (40N west + 10N west)

                   =                              10N west .