Level 2
Adam has 90 red stickers.
He has 3 times as many red stickers as blue stickers.
After he buys an equal number of red and blue stickers,
the number of red stickers is 2 times that of the blue stickers.
Level 2 PSLE A box contained black balls and green balls. 40% of the balls were green. After some red balls were added to the box, 28% of the balls were green. What percentage of the balls in the box were red?