Using Array within Solve Block

[yakpol]

Hi, I am a relatively new user of mathcad and not sure of its capabilities. I am trying to solve a system of three equations. Each equation contains arrays which are dependent on the solution/variables. I am getting an error message: "indexed assignment to a matrix element is not permitted in a solve block".
It's a kind of a sad limitation, wonder if there's a way around it. Please see file attached.

Thank you!

Yakpol