Answer:
At most 38 text messages.
Step-by-step explanation:
Let x represent number of text message you send or receive.
We have been given that the cell phone plan charges $.13 for each text message you send or receive. So amount charged for sending or receiving x text messages would be [tex]0.13x[/tex].
We are also told that your cell phone plan cost $39.99 per month, so total cost of monthly bill would be [tex]0.13x+39.99[/tex].
Since you can spend at most $45, so total cost of x messages should be less than or equal to 45 as:
[tex]0.13x+39.99\leq 45[/tex]
[tex]0.13x+39.99-39.99\leq 45-39.99[/tex]
[tex]0.13x\leq 5.01[/tex]
[tex]\frac{0.13x}{0.13}\leq \frac{5.01}{0.13}[/tex]
[tex]x\leq 38.5384615[/tex]
Therefore, you can send or receive at most 38 text messages.