Answer
1.76 g/L
Work Step by Step
The formula is d = PM/RT. First we need the molar mass of NO2:Nitrogen is 14g/mol and O is 16g/mol so we have 14 + 2*16 = 46g/mol. Then we convert the 35C to Kelvin by adding 273, which is 308K.
d = (0.970 atm * 46g/mol) / (0.0821 * 308K) = 1.76 g/L