The service plans are illustrations of linear equations
It will take 125 minutes for the plans to have the same cost
<h3>How to determine the number of minutes</h3>
From the question, we have the following parameters
<u>Service plan 1</u>
- Monthly fee = $16
- Charges = $0.15 per minute
<u>Service plan 2</u>
- Monthly fee = $21
- Charges = $0.11 per minute
So, the linear equations for both plans are:


When the plans cost the same, we have:

Collect like terms

This gives

Solve for x

Hence, it will take 125 minutes for the plans to have the same cost
Read more about linear equations at:
brainly.com/question/14323743