Explanation:
I'm not too sure but I would find the molar mass of nitrogen dioxide and then divide.
N - 14.01
O - 16.00
(14.01) + 2(16.00)
14 01 + 32.00 = 46.01
14.01 / 46.01 = 0.3044....
30.4%
32 / 46.01 = 0.6955....
69.6%
