9514 1404 393
Explanation:
From your knowledge of the world, you know that ...
- the cost of multiple items is the sum of their individual costs
- multiplication can be used for repeated addition
- utility fees are the sum of fixed fees and usage-related fees
- for a phone plan, text message costs are a usage-related fee
The problem statement asks for the cost of a single text message. For the purpose of finding that value, it is convenient to represent it using the variable t. The problem statement says Eric was billed for 450 text messages, so we expect his usage-related fee to be 450t, the sum of the costs of 450 messages--using multiplication for the repeated sum.
The problem statement says Eric was billed 12.50 for fixed fees. So, we expect Eric's total bill to be ...
fixed fees + usage-related fees = 12.50 + 450t
The problem statement says Eric's total bill was 35.00, so we assume that is the sum of the above-listed fees. That is, the two ways to express Eric's total bill are equal.
12.50 +450t = 35.00
