Chessisthebest so basically, the farmer took 120 grapefruits and x oranges. 1/10 (10%) of grapefruits look like oranges and 1/10 (10%) of oranges look like grapefruit. also 1/5 (20%) of all fruit looks like grapefruit (this incl. 90% of grapefruit - i.e. 108 grapefruits and x/10 oranges.) if we make an equation, we should have x+120/5 = x/10 + 108. if you solve this equation, you should get the answer of 840.
