If 60 is added to one-third of a number, the resulting value is double the number. What is the number?

Question

two frog live together in a backyard pond. One frog croaks every 4 minutes, the other croaks every 2 and 1/2 minutes. If they both croak together at 11am, what is the first time after 1pm that they will croak together?

Answer 1

If the number is n then n/3+60=2n, 60=5n/3, 5n=180, n=36.