speed of sound in oxygen(o2) at a certain temperature is 460m/s. the speed of sound in He at the same temperature will be( assume both gases are ideal)

Speed of sound in gases is given by square root of(yRT/M) where y is adiabatic constant, T temp and M molecular mass of the gas. Here temp not given so you can take it out from given value of oxygen and then put it for helium. Also care must b taken for `y` as oxygen is diatomic gas having y=7/5 and helium monoatomic gas having y=5/3. Hope you can solve now.