An algebra problem by varun satheshkumar

If you were 3 years old and your cousin was 5 times ay your age then, your cousin is 15 years old. The difference is 12. Now you are 79 years old.

79+12=91

If your cousin is 5 times your age when you are three, then your cousin is 15. Since your cousin is 12 years older than you, when you are 79, your cousin is $79+12=\boxed{91}$