Answer:
36
Step-by-step explanation:
The maximum height is the y-coordinate of the vertex
given a quadratic in standard form : ax² + bx + c : a ≠ 0
then the x-coordinate of the vertex is
= - 
y = - x² + 20x - 64 is in standard form
with a = - 1, b = 20 and c = - 64, hence
= -
= 10
substitute x = 10 into the equation for y
y = - (10)² + 20(10) - 64 = 36 ← max height
The correct answer is B.
Explanation
Since each interval mark is 1/4 of a unit, we will write this as 0.25. For the first point, 4 interval marks to the left of the y-axis makes it a negative number; 4(0.25) = 1; this makes the x-coordinate of this point -1. 2 interval marks above the x-axis makes it positive; 2(0.25) = 0.5; this makes the y-coordinate 0.5. This makes the first ordered pair (-1, 0.5).
The second point is on the y-axis. This makes the x-coordinate 0. It is 5 intervals above the x-axis; this makes it positive. 5(0.25) = 1.25 will be the y-coordinate, making the point (0, 1.25).
The third point is 3 intervals to the right of the y-axis; this makes it positive, and 3(0.25)=0.75 for the x-coordinate. It is 3 intervals below the x-axis; this makes it negative, and 3(0.25) = 0.75, making the y-coordinate -0.75. This puts the third point at (0.75, -0.75).
For this case we propose a system of equations:
x: Represents the amount of small popcorn tubs
y: Represents the amount of large popcorn tubs
According to the data we have to:
(Spending all the money in your wallet)
(Buying 7 popcorn tubs)
From the second equation we have:

Substituting in the first equation:

Thus, Katie can buy 3 large tubs of popcorn.
So:

In addition, you can buy 4 small tubs of popcorn.
Answer:
3 large popcorn tubs.
4 small popcorn tubs.