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 <em>t</em>. 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
