You can put this solution on YOUR website! Admittedly you can probably get better answers from other tutors on here but this is my mind's process solving this problem:
The teacher is 37, the student is 11. That's a difference of 26 years. So, 26 has to be the age of the student when the teacher is twice that, or 52; and as you can see, student and teacher will reach those ages in 15 years.