Chapter 1, Equations and Inequalities - 1.5 Use Problem Solving Strategies and Models - 1.5 Exercises - Problem Solving - Page 39: 28a

Less than 150 but not more than 100 messages.

Let x = Text messages y = Monthly bill For the table attached below, we used the equation: $\$40 + 0.10\times x=y$ When the monthly bill is $\$53.80$, that means that the number of messages you sent is somewhere between 100 and 150 messages.