300
The word problem that can be solved with d x 3:
Joe bought 3 fewer cupcakes than Sue, d is the number of cupcakes Sue has.
Joe bought 3 of each kind of cupcake, d is the number of kinds of cupcakes.
Joe bought 3 more cupcakes than Sue, d is the number of cupcakes Sue bought.
What is Joe bought 3 of each kind of cupcake, d is the number of kinds of cupcakes.