Question

this graph shows how the amount of cheese dominic has left is related to the number of sandwiches he makes.
pieces of cheese remaining
if dominic makes 80 sandwiches, how many pieces of cheese will he have left?
20 pieces
30 pieces
10 pieces
40 pieces

Explanation:

Step1: Locate x=80 on the x - axis

The x - axis represents the number of sandwiches. We find the value 80 on the x - axis (number of sandwiches) scale.

Step2: Find the corresponding y - value

From the point x = 80 on the x - axis, we move up (or follow the graph) to find the corresponding y - value (pieces of cheese remaining). Looking at the graph, when the number of sandwiches is 80, the number of pieces of cheese remaining is 10? Wait, no, wait. Wait, the graph: when x = 0, y = 90; when x = 90, y = 0. Let's check the slope. The slope $m=\frac{y_2 - y_1}{x_2 - x_1}=\frac{0 - 90}{90 - 0}=- 1$. So the equation is $y=-x + 90$. When x = 80, $y=-80 + 90 = 10$? Wait, but looking at the graph, when x = 80, the point on the line: let's check the grid. Each square: x - axis: from 0 to 100, with each major grid line at 10,20,...90,100. y - axis: 0,10,20,...90,100. The line goes from (0,90) to (90,0). So when x = 80, we go up from x = 80 (which is 8 units from 0 on the x - axis, each unit is 10? Wait, no, the x - axis is labeled 0,10,20,...,90,100. So each tick is 10. So x = 80 is at the 8th tick (0 is 0, 10 is 1, ..., 80 is 8, 90 is 9). The y - axis: 0,10,20,...,90. The line from (0,90) to (90,0). So when x = 80, y = 90 - 80=10? Wait, but let's check the graph. If we look at the graph, when x = 80, the point on the line is at y = 10? Wait, no, maybe I made a mistake. Wait, the graph: when x = 0, y = 90; x = 10, y = 80; x = 20, y = 70; ... x = 80, y = 10; x = 90, y = 0. Yes, so the pattern is y = 90 - x. So when x = 80, y = 90 - 80 = 10.

Answer:

10 pieces (the option "10 pieces")