I don't get it how to do it it hard

What is the final velocity of the initial velocity of 25 and -50?

Aperson stands on a platform, initially at rest, that can rotate freely without friction. the moment of inertia of the person plus the platform is ip. the person holds a spinning bicycle wheel with its axis horizontal. the wheel has moment of inertia iw and angular velocity ωw. take the ωw direction counterclockwise when viewed from above. part a what will be the angular velocity ωp of the platform if the person moves the axis of the wheel so that it points vertically upward?

Wavelength,frequency,and energy are related.what happens to a wave as it’s wavelength gets shorter?