Chrisrina had four times as much money as her brother Kyle, but when their grandmother gave each of them twenty dollars, Christina had twice as much as Kyle. How much did each have orginally?

Originally: C = 4K

After: C + 20 = 2(K + 20)

Use the first in the second:

4K + 20 = 2(K + 20), or 4K + 20 = 2K + 40 so K = 10

Use this in the first equation. C = 4*10 or C = 40

Hence Kyle originally had 10 dollars and Christina originally had 40 dollars.