Answer:
You need 8,53 L of ammonia
Step-by-step explanation:
Global reaction of remotion of nitrogen oxide with ammonia is:
4 NH₃ + 6 NO ⇒ 5 N₂ + 6 H₂O
This balanced equation shows that 4 NH₃ moles reacts with 6 NO moles.
With 100% yield and temperature and pressure constants it is possible to apply Avogadro's law. This law is an experimental gas law relating the volume of a gas to the amount of substance of gas present. The formula is:

Where:
V₁ is the NO volume = 12,8L
n₁ are NO moles = 6
n₂ are NH₃ moles = 4
V₂ is NH₃ volume, the unknown.
Thus, V₂ are 8,53 L of ammonia
I hope it helps!