Suppose that a box is being towed up an inclined plane as shown in the figure. find the force w needed to make the component of the force parallel to the inclined plane equal to 2.5 lb. give answer in component form.

You need to find, first, the horizontal component of the inclined force (call it Wx), using an angle of 15 degrees (which is the angle between the inclined plane and the horizontal).

=> cos(15°) = Wx / 2.5 lb => Wx = 2.5 lb * cos(15°).

Second, you can find the inclined force , W, needed to produce the horizontal component Wx.

cos(33°) = Wx / W => W = Wx / cos (33°) = 2.5 lb*cos(15°) / cos(33°) = 2.88 lb

2.88 lb 

Really long apparently