At the same temperature and pressure, the molar mass ratio of two gases is equal to the density ratio. Can you teach me the formula?

At the same temperature and pressure, the molar mass ratio of two gases is equal to the density ratio. Can you teach me the formula?

Let m be the molar mass, m the mass of matter, p the pressure of gas, V the volume of gas, n the quantity of matter, r the molar constant of gas, which is a constant, t the Kelvin temperature
PV1=n1RT,PV2=n2RT.
N = m / m, where PV1 = (M1 / M1) RT, PV2 = (m2 / m2) rt and density ρ = m / V, then PM1 = ρ 1rt, PM2 = ρ 2rt;
Comparing the two formulas, M1 / m2 = ρ 1 / ρ 2 is obtained