How long would it take if the both worked to make 125

Question

It takes Fred 3 hours to prep 125 sandwiches at the sandwich shop. When John performs the same task, however, it takes him an extra hour. If both of these individuals were assigned to do the job together, how long would it take both or them to produce 125 sandwiches?

Answer 1

Fred needs 3 hours. John needs 4 hours

t represents the time they work together

(t / 3) + (t / 4) = 1 1 represents the 1 whole job

Can you solve for t and answer?