Crystal earns $5.50 per hour mowing lawns.
• write a rule to describe how the amount of money m earned is a function of the number of hours h spent mowing lawns.
• how much does crystal earn if she works 3 hours and 45 minutes?

 For this case, the first thing we must do is define a variable:
 h: number of hours worked.
 We now write the equation that models the problem:
 
 So, for 3 hours and 45 minutes we have:
 
 Remember that we have the following conversion:
 1 hour = 60 minutes
 Substituting values:
 
 
 Crystal earns about:
 m = $ 20,625

Yes, two vertical lines can be complementary