Can someone help me please? This is very confusing. =S

Prove that the three medians of a triangle are concurrent by choosing as vertices A(6a,6b) B(-6a-6b) and C(0,6c) and following these steps:

a) Find the Midpoints P,Q and R of BC, CA and AB respectively. Show that the median through C is x=0 and find the equation of the other two medians.

b) Find where the median through C meets another median, and show that the point lies on the third median.

Thanks