Respuesta :
The least common multiple would give you the answer you are looking for.
Multiples of
6: 6, 12, 18, 24, 30, .....
9: 9, 18, 27, 36, .....
He will have a lesson on the same day in 18 days.
Starting on Tuesday we need to go 18 days. 14 days would be another Tuesday, Wednesday = 15, Thursday = 16, Friday = 17, Saturday = 18
Multiples of
6: 6, 12, 18, 24, 30, .....
9: 9, 18, 27, 36, .....
He will have a lesson on the same day in 18 days.
Starting on Tuesday we need to go 18 days. 14 days would be another Tuesday, Wednesday = 15, Thursday = 16, Friday = 17, Saturday = 18