2NH3 is equivalent to N2 + H6 since the 2 at the beginning gets distributed to both atoms. Knowing this you can rewite the equation as
H2 + N2 = H6 + N2
The N2 can cancel out leaving
H2 = H6
You now have to ask ‘2 times what equals 6?’ The answer is obviously 3 at this point.
Answer: C. 3
they cannot influence each other
