Question

Your friend’s piano lesson lasts 15 minutes longer than your piano lesson. You have 6 lessons per month and your friend has 4 lessons per month. At the end of the month, your time spent at piano lessons is the same as your friend’s time. How many minutes is your friend’s piano lesson?

Answer 1

Assume your friend piano time is x min, so your piano time is x-15 min.
6×(x-15)=4x
6x-6×15=4x
6x-4x=90
2x=90
x=45 min