Plastic storage bins are designed so they can be nested. the picture shows how each one fits inside another, leaving only the top part showing. the 4 stacked 10-gallon bins shown here measure 29 inches high. the height of the stack grows at the rate of 4 inches for each added bin. 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.

One may note, you kinda missed including the related pictures.

so for every added bin, the stack grows by 4 inches. rise/run, the run is 1, the rise is 4, 4/1 = m = slope

now.... in the picture not shown hehee, the 10-gallon bins, 4 of them measure up to 29 inches high.... wait a second.. I thought the rise was only 4?

well, there are 4 bins, like in this case, so the rise should be 4*4, or 16, but there are 29 inches, that means, the slack leftover is the "initial value", or y-intercept, which should be 29 - 16, or 13.