a The exercise gives us a function that describes the cost in dollars of buying x tickets to the orchestra, using a $10 coupon.
C(x)=17.5x-10
In the above formula, C(x) represents cost, in dollars, and x represents number of tickets. Calculating the cost of buying five tickets is the same as evaluating C(x) for x=5. To do so, we substitute 5 for every instance of x in the function.
With a $10 coupon, it costs $77.50 to buy 5 tickets to the orchestra.
b In Part A, we were given the number of tickets and needed to calculate the cost. This time we are given the cost, and need to calculate the number of tickets.
C(x)=17.5x-10
Calculating the number of tickets that can be bought with $ 130 means that we will need to substitute this amount for C(x) in the function, and solve for x.
