extract variables from string

let say,i have a string:

"Given P = 100 kpa, V = 2 litres, T = 273 K, R = 8.314 Solve for n."

how can i extract all variables in it?

[Rik]

As you stated yourself already, this is not a trivial task. It seems more effective to have the same discussion there, instead of splitting attention over the two threads.