Answer:
t = 10b + 10c
Explanation:
As stated in the problem, 1 bag holds 10 doughnuts so that give us 10b since we don't know how many bags were bought/sold but we do know how many comes in each. Same goes for cartons.
Were asked to write a formula for t, and since we don't know how many bags(b) or cartons(c) were sold, our t remains t.