To solve this problem you must apply the proccedure shown below:
1. Clear the radius from the formula for the circumference of a circle and substitute values, as following:

2. Substitute the radius calculated into the formula for calculate the surface area of the sphere:

The answer is: 
Answer:
<h2>
<u>$52.5</u></h2>
Step-by-step explanation:
Step one:
given data
we are given that the linear function for the cost is c=3.5t
c is the cost and
t is the number of tickets.
We are told that t=15, to find c, let us put the value of t in the linear function for the cost

<u>This shows that 15 tickets will cost $52.5</u>
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1 hour = 60 minutes
60 minutes / 10 minutes = 6
So 6 times in one hour 3 buses depart.
6 x 3 = 18 total buses in an hour.