Answer:
The expression is equal to 
Step-by-step explanation:
Let
x ----> the number of hours that the roller blades are rented
y ----> the cost of renting roller blades in dollars
we know that
The linear equation in slope intercept form is equal to

where
m is the slope or unit rate of the linear equation
b is the y-intercept or initial value of the linear equation
In this problem we have
The slope is equal to

The y-intercept is equal to
----> value of y when the value of x is equal to zero
substitute

For x=h hours
substitute

Slope intercept form: y = mx + b
mx = slope
b = y-intercept
We know the y intercept is 0, so nothing will be written there.
To find the slope of this line, we can use the slope formula.

We'll use the points (1, 0) and (3, 1) to find the slope.
Now we can just plug these values into the equation to find the slope.
1 - 0 / 3 - 1
1 / 2
The slope of the line is 1/2, or 0.5.
The slope-intercept form of this line can be written as:
y = 0.5x
6+9=15
y+9=x
x=30
y+9=30
y=21
7/21 or 1/3rd, it's just a ratio of white to all, there's 7 white straws and 21 in all, then you can simplify it down to 1/3rd.