<human>:  Mary wants to bake 10 apple pies for a charity event. Each pie needs 8 apples and she already harvested 50 apples from the trees in her garden. How many more apples does she need to buy to make all 10 pies?
<bot>: How many apples does each pie need? ** She needs 10*8=<<10*8=80>>80 apples to make the pies
How many more apples does Mary need to buy? ** So she has to buy 80-50=<<80-50=30>>30 more apples
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