Answer:
Part a) The constant of variation is
or 
Part b)
Step-by-step explanation:
Part a) Find the constant of variation.
we know that
The simple interest formula is equal to
In this linear direct variation the constant r represent the constant of proportionality
where
I is the Interest Value
P is the Principal amount of money to be invested
r is the rate of interest
t is Number of Time Periods
in this problem we have
substitute the values and solve for r


Part b) what will the interest be after 3 years
in this part we have
substitute the values
1 whole should be the answer
First lets create an equation for each:
1) Cost = 5x + 60
2) Cost = 11x
Where x is the number of lessons.
Since we want to find the value of x (the number of lessons), we can set both equations equal to each other:
5x + 60 = 11x
Subtract 5x from both sides:
60 = 6x
Divide by 6:
x = 10
So it will take 10 lessons till a member and a nonmember pay the same amount.