Hello. The image I sent is a mathematical inequality from an article. Pmax_chp is a scalar. Pt_chp is a variable. Phk_chp is a variable. Pht,k_chp,u is a variable.

If I want to implement the formula inside the red box in GAMS, how can I simultaneously maximize these two expressions while they are separated by commas and I am still coding and the code continues?

Hi, I think you’ll need to do some reformulation, such as using the Big M method (for example). However, this is due to the nature of the problem and not related to GAMS.
There are surely multiple ways to implement the equation.
Another important piece of information is the meaning of each index and subscript. For example, the variable Ph appears several times with different sets: (t, CHP, u); (k, CHP); and (t, k, CHP, u).
I hope this helps you a bit more.
Best regards,