Answer:
$10 each
Step-by-step explanation:
There are four friends
Friend 1 = $15
Friend 2 = $20
Friend 3 = $40
Friend 4 = unknown
NOTE;
You didn't provide the earnings of the fourth friend is not given BUT the question can be solved without knowing the earnings of the fourth friend
The four friends decide to split their earnings equally among themselves
how much will the friend who earned $40 give to the others?
Amount given to others = $40 / 4
= $10
The friend who earned $40 will give $10 each to the others