Question

In the chemical formula 2NO2 how many atoms ot oxygen are there

Answer 1

Four O atoms bc in one NO2 molecule there are 2 O atoms, so in two NO2 molecules there would be four :)

Answer 2

I think there are four total.
This comes from adding the 1 O from the NO to 2O from the O2. However the oxygen needs to be balanced.
Multiplying the left NO and the NO2 on the right side by 2 you get:
2NO + 2O -> 2NO2
Left to Right:
2 x 1 N =2N -> 2 x 1 N = 2N

2x(One) Oxygen+ O2 (Two Oxygen) = Four Oxygen or 4O