When the lesson is scheduled, the hourly rate will be multiplied by the duration of the lesson, which will result in the desired cost.
Divide the desired cost for the lesson by the duration of the lesson to get the hourly rate.
Desired cost of $60 for a 1.5 hour lesson
$60 divided by 1.5 equals $40.00 per hour
Desired cost of $45 for a 50 minute lesson
$45 divided by 50/60 equals $54.00 per hour
NOTE: If your hourly rate has a repeating decimal, it's important to make sure you include 4 decimal places so the system rounds the number to the full value.