You need to notice that you need to decompose the weight into two components, one along x axis, that is parallel to the inclined surface of the plane and one along y axis, that is perpendicular to the inclined surface.

You need to use the component that is parallel to x axis, hence, you need to set up the following equation, using the information provided by the problem, that the cable withstands 2,25 pounds, such that:

`W*sin theta = 2,25 => W = (2,25)/(sin theta) `

Since the problem provides the angle `theta = 21.5^o` , yields:

`W = (2,25)/(sin 21.5^o) => W = (2,25)/(0.366) => W = 6,147` pounds

Hence, evaluating the weight of the heaviest piece that can be pulled up the ramp, without friction yields `W = 6,147` pounds.