What's the use, you are going to fail EC223 anyway. Indeed, gec223 = -80+3tec223 and tec223 ≤ 20, so gec223 ≤ -20. Also, what is 20ptec233?

More seriously, this is the wrong way to ask a math question. Apparently, you copied and pasted the text from some source without bothering to proofread it, improve or explain the notation. Why are people supposed to guess that in tec233, t denotes time and ec233 refers to the name of the course EC233? Is it suppose to be something like ? Next, which Lagrange theorem are you referring to? Do you mean the method of Lagrange multipliers? Last but not least, have you tried solving the problem? Have you looked at the solution of similar problems? What exactly is your difficulty?