Answer:
Part a) 
Part b) The total cost is 
Part c) see the explanation
Step-by-step explanation:
Part a) Write a linear equation to represent this situation
Define the variables
Let
x ----> the number of hours
y ----> the total cost in dollars
we know that
The linear equation in slope intercept form is equal to

where
m is the slope or the unit rate
b is the y-intercept or initial value (value of y when the value of x is equal to zero)
In this problem we have that
The unit rate or slope is equal to

The y-intercept or initial value is equal to

substitute

Part b) Use the equation to find the total cost to rent skis from 8:30 am to 3:00 pm
Remember that
3:00 pm=15:00
so
from 8:30 am to 3:00 pm, the total hours is equal to
15:00 -8:30=6:30=6.5 h
For x=6.5 h
substitute in the linear equation and solve for y

Part c) What does your answer mean in context of the problem?
we have that
y=220.25
That means -----> The total cost to rent skis for 6.5 hours is equal to $220.25