When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is

10 time smaller

Explanation:

Since the average force of impact is the impulse divided by the time of impact:

whereas impulse is the change of momentum (from full to rest) which is constant and independent of the time of impact. So if you make the time of the impact about 10 times as great as for a stiff-legged landing, the average force that you experience would be 10 times smaller.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.