Question

The rate of change is 2. It represents a decrease in the amount of raspberries in the bucket for each batch Iris makes.
Substitute z = 1 and y = 16 into the equation.
7
4
y = mx + b
y=-2x+b
?
2(?
+b
1
16
X
Batches, z
Raspberries Left in Bucket (cups), y
1
16
4
10

Answer 1

You have slope m = -2 (a decrease of 2 cups per batch). Use the point (z, y) = (1, 16).

Substitute into y = mx + b (use x = z):
16 = -2(1) + b
16 = -2 + b
b = 18

So the equation is y = -2x + 18 (or y = -2z + 18).
Check: at z = 4, y = -2(4) + 18 = 10, which matches.