Answer:
+4
Explanation:
Hello,
In this case, considering nitrogen dioxide's formula:
[tex]NO_2[/tex]
And due to the fact that oxygen's oxidation state is -2 in this case, we could find nitrogen's oxidation state in nitrogen dioxide by using a balance charge:
[tex]N^{+x}O_2^{-2}\\x-4=0\\x=4[/tex]
For that reason, nitrogen's oxidation state is +4:
[tex]N^{+4}O_2^{-2}[/tex]
Best regards.