Buffers questions!

Hi everyone...

I seriously do not get buffers!!! They are so complicated. I just had an equilibria test and had no idea how to go about the following three questions...

Please help me out?

(1) State and explain whether a 1.0 dm^3 solution of 0.10 mol NH3 and 0.20 mol HCl will form a buffer solution?

(2) State and explain whether a 1.0 dm^3 solution containing 0.20 mol NH3 and 0.10 mol HCl will form a buffer solution?

(3) Explain how you would prepare a buffer solution of pH 3.75 starting with methanoic acid?
For this question, a previous part asked me to calculate the Ka value, [H^+] and pH which were: Ka = 1.78 x 10^-4, [H^+] = 1.33 x 10^-3 and pH = 2.87

Thank you everyone