N's 2nd law: an eq'n for acceleration 'a'

Hello!

I was given two formulae for my Physics lab: ma=mg-T and T=Ma (using a pulley).

ma--> net force on small object (paper clip)
M--> larger mass (glider)
mg--> force of gravity
a--> acceleration
T--> tension of ribbon used

I'm supposed to combine the two equations to get one equation for acceleration. I thought about arranging them this way, but I think I'm wrong:

T=Ma (1)
T=mg-ma (2)
0 = -mg + (Ma+ma)

(the last part is difinitely messed up!)

Hope some can help me out!