Answer: 45 minutes for BOTH workouts
Step-by-step explanation:
Let time for plan a be x
Let time for plan b be y
On Wednesday
# of clients for plan a are 5
# clients for plan b are 3
On Thursday
# of clients for plan a are 7
# of clients for plan b are 9
Wednesday eqn --> 5x+3y=6
Thursday eqn --> 7x+9y=12
Multiply Wednesday equation by -3 and use elimination to solve
-15x-9y=-18
7x+9y=12
-8x=-6
x=6/8
Reduce: x=3/4 hour
Substitute x=3/4 into Thursday equation
7(3/4)+9y=12
9y=27/4
y=3/4
Therefore, the length of BOTH the plan a and plan b workouts were 45 minutes