Answer:
C.
Step-by-step explanation:
This is a multi-step equation, considering that there are three steps.
Step 1: 17 x 0.51. There are 17 light envelopes, so multiply these two numbers and you will get 8.67.
Step 2: 13 x 0.73. 13 heavy envelopes means to multiply 13 by the cost, which is 0.73. This should get you 9.49.
Step 3: Add the two numbers to get the total cost. 9.49 + 8.67 = $18.16.
