Plastic storage bins are designed so they can be nested. four 10-gallon bins stacked together measure 26 inches high, and 9 stacked bins measure 41 inches high. write an equation in the form y = mx + b to describe the relationship between x, the number of nested bins, and y, the height of the stack

First, you need to know the coordinates of the points:

If x is 9 stacked bins to the y of 41 inches, the first point is (9,41)
From there, you can determine the other point: (4,26)

Find the slope by subtraction using the formula: y2-y1/x2-x1

(41-26)/(9-4)
15/5
slope is 3

y=3x+b

To find b, substitute one point into the equation. I will use (4,26)

26=3(4)+b
26=12+b
-12  -12

b=14

Your final equation is:
y=3x + 14

In this problem it decreased 20%