That's not right.Yes
You cannot directly subtract the magnitudes of the velocity from each other. This only works when the velocities are pointing in the same direction.
The total velocity of the apple when it starts its journey is 8.731m/sec. And it is pointed at a 20 degree elevation, right toward the trash can. In the x-y plane, it will have a straight line course, in the plane drawn between z and the direction of travel, it will have a standard parabolic ballistic trajectory.
You can answer part C based on the initial angle and initial velocity.
For part B, you need to break the velocity into components, x- component, y-component, z-component. Double check your components with
##v_x ^2 + v_y^2 + v_z^2 = V^2 ##.
Once you have components, you can directly subtract the velocity from the bike -- component-wise. That way you are only dealing with velocities in the same directions.
Review the posts in this thread. There have been at least a couple people who have posted the correct answers...and quite a few who have posted incorrect methods.