Question

Deshaun the trainer has two solo workout plans that he offers his clients: Plan A and Plan B. Each client does either one or the other (not both). On Monday there were 7
clients who did Plan A and 9
who did Plan B. On Tuesday there were 5
clients who did Plan A and 3
who did Plan B. Deshaun trained his Monday clients for a total of 12
hours and his Tuesday clients for a total of 6
hours. How long does each of the workout plans last?

Answer 1

Let A and B represent the number of hours that plans A and B last, respectively. Then the problem statement tells you
  7A +9B = 12
  5A +3B = 6

There are many ways this set of equations can be solved. I find it fairly simple to use a graphing calculator. The one shown tells me the workouts are each 3/4 of an hour.

Plan A lasts 45 minutes (3/4 hour)
Plan B lasts 45 minutes (3/4 hour)