for the reation: B203 + 3Ca = 2B + 3 CaO

how do i attempt to know which 1 is oxidized?

I really do not understand chemistry its my weakest subject

You assign oxidation numbers, based on the scheme in the material you asked for yesterday, to all of the elements. Then, the ones that lose electrons are oxidized and the ones that gain electrons are reduced. For example,

B is B2O3 is +3 each and O in B2O3 is -2 each. Ca is zero (any element in its free state is zero). Etc. We'll be happy to help you if you get lost.