At the movies a bag of popcorn cost $3.50 and a bottle of water coast $2.75. If Madeline has $18 and bought two bottles of water how many bags of popcorn can she buy at most

Multiple the cost of the water bottle ($2.75) then whatever you answer is, you subtract that from 18. She should have $12.5 left. The most bags of popcorn she could get is 3. Just add $3.50 until it's closes to the amounts of money she has left.