Answer:
2
Step-by-step explanation:
Since you are balancing the equation you need to have equal amounts of each element on each side. Right now there is 2n and 2o on one side, and on the other 2n and 1o. Although the number of n's on each side is equal the number of o's are not. First I balance the number of oxygen's on each below, but doing that made the number of nitrogen's unbalanced. So then I balanced the nitrogens in step 2.
__N2+ __O2 = __N2O
1. __N2+ __O2 = 2 N20
2. 2 N2 + 1 O2 = 2 N2O