If Z_13 = F and V_F = span ((1,1), (1,2)), how many elements does V_F have?

I can find nothing in my book or on the internet that explains how to do this. Please help! Thanks in advance!

I understand that the general form for all vectors in the vector space is (a+b, a+2b) for this particular span. This means that the components of the vector can't be the same, so would it be 156 instead? You wouldn't be able to have (0,0), (1,1), (2,2), etc. Is this correct?