Let us represent the number of tickets bought with t, the number of drinks bought with d, and the number of bags of popcorn bought with b. The expression for total cost becomes,
6.5t + 5.5d + 6b
We know that two tickets were bought, so we may plug in 2 for t and get the final expression:
6.5(2) + 5.5d + 6b
13 + 5.5d + 6b