The graph shows the relationship between the volume of a rectangular prism and the volume of a square pyramid with an identical base and height. what is the slope of the line?

The picture in the attached figure

we know that
volume of a rectangular prism=area of the base*h
area of the base=B
volume of a rectangular prism=B*h-----> equation 1

volume of a square pyramid=(1/3)*area of the base*h
area of the base=B
volume of a square pyramid =(1/3)*B*h-----> equation 2

substitute equation 1 in equation 2
volume of a square pyramid =(1/3)*volume of a rectangular prism
volume of a rectangular prism/volume of a square pyramid=3

therefore
the slope of the line must be 3

let's check it
To solve for the slope of the line, you must choose two coordinates first and use the formula m = (y₂-y₁)/(x₂-x₁). 
Choosing the points (2,6) and (3,9) :m = (9-6)/(3-2) = 3.

the answer isThe slope of the line is 3.