Make solve block give approximate solution for trial and error

Hello,

I'm having a problem finding the solution for a set of equations. Using MathCad Prime 10

The usual method for solving this exercise is to due a iterative process assuming values for L4 and verifying for which value one of the equations is the closest to 0.

I can do it manually inside of mathcad but have not made the solve block do it for me.

Is this because the solution is approximate?
I am attaching the mathcad file.