how do I solve simultaneous equation with 3 unknowns ?

[DanB1983]

I would recommend reading up on Gaussian elimination (and Gauss-Jordan elimination).  This should be fairly straightforward to implement in LV, provided all your equations are of the form shown in your example.

You will need to get your equations in the form where one side equates to zero.

I.e. in your example

4X - 2345r = 0
5X + 4V + 21r = 0
2X - V = 0

[altenbach]

I don't see the quadratic part you mentioned earlier.

[Joseph_Loo]

Your equation has the trivial solution of x=v=r=0.

[rattlesnake]

A set of independent equations in two or more variables is called a simultaneous equation. To find the value(s) of the variables for which the set of equation holds is called solving the equation. There are different methods used to solve simultaneous equations.

Methods like Elimination and substitution will help you a lot .

Or else you can find a simultaneous equation solver