calculate the pH of a buffer made by combining 50.0mL of 1.00M ammonia and 50.0mL of ammonium nitrate Kb=1.77x10^-5

Thank you very much i came out with pH=9.25

What did you use for the concn of NH4NO3? The problem can't be solved without that.

I assumed it was 1.00M

You can't make that assumption. It should be given in the problem (or at least some way to calculate it); otherwise the problem can't be solved.

It was given no where in the problem. I have no choice but to make that assumption if i leave it blank and try nothing i get no points for effort even if it's professor error I've been down that road with him before i worked the problem and stated my assumptions in a side note so he would see i tried. By doing that i should receive full credit for it.

1.00 M is the concentration. M=mol/L which is concentration. 9.25 is correct!

Use the Henderson-Hasselbalch equation.

pH = pKa + log[(base)/(acid)]
base = NH3
acid = NH4NO3
Ka = Kw/Kb