Solving for equations the HP50, 49.. way.

[Luigi Sardella]

With the RPN based HP calculators (UP48,..50) one could define an expression, or equation with several variables; give it a name; and then solve for one of the variables, assigning values to the others. It worked also inside a program, with the ROOT command.
Can I do the same with my new Prime, and how? The documentation I have read is scanty and unclear; all trials I made EXPORTing code snippets and variables have been met with Syntax Error flags.
Thank you for help.