Question

A buffer solution contains 0.120M acetic acid and 0.150M sodium acetate.

Answer 1

A. M x L = moles. 
b. CH3COOH + NaOH ==> CH3COONa + H2O 
I...6 mmols....0.......7.5 mmoles 
C... 0........0.51 mmols..0 
E...6-0.511 ....0.......7.5+0.511 

I stands for initial 
C stands for change. 
E stands for equilibrium. 
Just divide mmoles by 1000 to convert to moles. I work in mmoles because I get tired of writing those zeros. 

c. done as in b.