Use of HP27s/19b and Plus42 solver

[Marco Polo]

I am very used to HP48/50 Multiple Equation Solver (MES) and i am managing to start using Plus42 even if it doesn't have something similar.
Just to start with something easy, i am playing with Ideal Gas Law.
In HP50 i have the following equations

Code:

{ 
'P*V=n*CONST(R)*UBASE(T)'
'm=n*MW'
}

This simple system considers UOM and allows the solution in case only moles or mass are required/available.
In Plus42 i tried to use the L function to reproduce MES behaviour

Code:

'P*V-L(n:m/MW)*8.31451_"J/gmol/K"*UBASE(T)*UVAL(n/n)'

but i cannot solve for 'n' (other variables work ok)

Am i doing something wrong or there is no way to get the score?

Thank you