90. A box contains yellow and white ping-pong balls. After removing 10 white balls, the number of yellow balls in the box is twice the number of white balls; after removing 9 yellow balls, the number of white balls in the box is five times the number of yellow balls. Initially, the box contains $\qquad$ yellow balls and $\qquad$ white balls.
Reference answer: 10,15
Key points: sum and difference, multiple relationships