How much faster does a helium atom travel than a nitrogen molecule at the same temperature?

The speeds of the two kinds of particles are related by the requirement that at the same temperature, their kinetic energies are equal. Strictly speaking, it is the average kinetic energy of two samples of the two gases that are equal, but we can find the answer by limiting ourselves to two particles and setting their kinetic energies equal.
Kinetic energy is related to mass and velocity by the equation
E_k = 1/2 mv^2
where Ek is kinetic energy, m is the mass of the particle, and v is its velocity. Your class may use different symbols for these quantities.
Your question—how much faster does a helium atom travel than a nitrogen molecule at the same temperature—can be answered by finding the ratio of their speeds at constant temperature. We will do this by writing the equation showing the equality of the two kinetic energies, and then performing some algebra to get the ratio we want.
Thus,
E_k(N_2) = E_k(He)
1/2 m_(N2)(v_(N2))^2 = 1/2 m_(He)(v_(He))^2
So,
(v_(He)/v_(N2))^2 = (m_(N2)/m_(He)) or
v_(He)/v_(N2) = (m_(N2)/m_(He))^(1/2) .
The mass of an average nitrogen molecule is about 28 amu, and the mass of the average helium atom is about 4 amu, so this evaluates to the square root of 28/4 or the square root of 7, which is about 2.65 according to my calculator app.
I have not said much to distinguish velocity (a vector) from speed (a scalar), but the square of velocity is a scalar quantity, so when we take the square root, we actually end up with the scalar speed.