Given that you have only two set of data, you can only assume a linear model.
To find the linear model (equation) that predict the number of cars (x) as a functionn of the parking fee (f) you follow, using only two set of data, follow this procedure:
1) Find the slope, m
m = [10 - 15] / [30 - 20] = - 5 / 10 = - 0.5
2) Use the slope-point equation
y - y1 = m (x - x1)
=> y - 10 = - 0.5 (x - 30)
=> y - 10 = - 0.5x + 15
=> y = - 0.5x + 15 + 10
=> y = - 0.5x + 25
or c = - 0.5 f + 25 <-------- equation
Now you can replace 6 for f to get the number of cars when the fee is $6
c = - 0.5 (6) + 25 = - 3 + 25 = 22 <---- this is the number of cars when fee is $6
The width is 18 because if you take 82 and subtract 10 for the 2 lengths ( because we are using perimeter) you come out with 72. 72 divided by 4 is 18, the lengths are five more because we took away that 5 in the beginning.
If the area of a parallelogram is given as with a height of , we can refer back to the equation for the area of a parallelogram: \displaystyle A= b \cdot h, where is height and is the length of the base.