Answer: plan A lasts for 1.25 hours.
Plan B lasts for 0.5 hour.
Step-by-step explanation:
Let x represent the number of hours that plan A lasts.
Let y represent the number of hours that plan B lasts.
On Friday there were 4 clients who did Plan A and 8 who did Plan B. Elsa trained her Friday clients for a total of 9 hours. This means that
4x + 8y = 9 - - - - - - - - - - - - -1
On Saturday there were 2 clients who did Plan A and 3 who did Plan B. Elsa trained her Saturday clients for a total of 4 hours. This means that
2x + 3y = 4 - - - - - - - - - - - 2
Multiplying equation 1 by 1 and equation 2 by 2, it becomes
4x + 8y = 9
4x + 6y = 8
Subtracting, it becomes
2y = 1
y = 1/2 = 0.5
Substituting y = 0.5 into equation 1, it becomes
4x + 8 × 0.5 = 9
4x + 4 = 9
4x = 9 - 4 = 5
x = 5/4
x = 1.25
