Thread: Amount/cost word problem

All paperback books cost d dollars each and all hardback books cost 2d dollars each. If Kate paid 7d dollars for 5 books, how many paperback books did she buy?

I'm having trouble setting up an equation to solve this. I know the answer should be 3.

let x = number of paperbacks purchased

dx + 2d(5-x) = 7d

x + 2(5-x) = 7

solve for x

Thanks skeeter! Makes so much more sense now!