The given equation, y = mx + b is the slope intercept form of a linear equation where
m represents slope
b represents y intercept
The slope represents the rate of change of the values of y with respect to x. The values of y in this case represents the cost of renting the car while x represents the number of days for which the car is rented. Therefore,
slope, m = $45
The y intercept is the value of y when x is zero. We can see that the initial fee is $85. This means that even if the car is rented for zero days, the initial fee of $85 must be charged, Thus, y intercept is 85
Therefore, the equation representing the cost, y, of renting the car for x days is
y = 45x + 85