Question 564170
take the sum both of them donated to be x, after both of them donated x amount, jack has 4 times the amount wilson has. So we can form this equation:4(21-x)=69-x
as jack has 4 times the amount wilson has, wilson has to multiply his amount left by 4 so that they will have the same amount.
4(21-x) is wilson's amount left.
(69-x) is jack's amount left.
so now we multiply 4 into (21-x) and that gives u (84-4x)
now put the x on the left and the amount on the right, so it gives u -4x+x=69-84. 
after u calculate, it becomes -3x=-15. 
so x=5.