I need help badly.

Question

It takes Brenda 3 hours ( working alone) to make sandwiches for a charity organization. Brian ran late and joined Brenda 1 hour later. If Brian worked alone it would take him 4 hours to make the sandwiches needed. How long will it take them to complete the job working together? [Hint: the number of sandwiches they make is irrelevant]

Answer 1

Brian worked for h hours

Brenda worked for h + 1 hours

h / 4 + (h + 1) / 3 = 1

3h + 4(h + 1) = 12

3h + 4h + 4 = 12

7h = 8

h = 8/7

Brian works for 8/7 of an hour and Brenda of 15/7 of an hour.

You can verify by substituting into the first equation.

You should get 2/7 + 5/7 = 1