Lenny is making his own laundry soap. The recipe calls for 2 parts borax, 2 parts washing soda, and 1 part soap flakes. If Lenny uses 7 cups of soap flakes, how many cups of borax and washing soda combined does he need?
7 CUPS
14 CUPS
28 CUPS
21 CUPS
Since the recipe calls for 2 parts borax for every 1 part soap flakes, Lenny would need 2 x 7 = <<2*7=14>>14 cups of borax.
Similarly, since the recipe calls for 2 parts washing soda for every 1 part soap flakes, Lenny would need 2 x 7 = <<2*7=14>>14 cups of washing soda.
Therefore, Lenny needs a total of 14 + 14 = <<14+14=28>>28 cups of borax and washing soda combined. Answer: \boxed{28}.