A box of cookies is shared among three children. Fernando gets 3 times as many cookies as Mary. Tessa gets twice as many cookies as Fernando. What fraction of the box of cookies does Fernando get?
Mary's number --- x
Fernando's number = 3x
Tess's number = 2(3x) = 6x
total = x + 3x + 6x = 10x
Fernando's share = 3x/(10x) = 3/10