T. P same: V1: V2 = N1: N2 Who can help me write down the derivation process of this chemical formula P * m / ρ = RT * m / m what's going on?

T. P same: V1: V2 = N1: N2 Who can help me write down the derivation process of this chemical formula P * m / ρ = RT * m / m what's going on?

pV=nRT
n=m/M
d=m/V