It's the one on the left. We're allowed any calculator that's not programmable and cannot store text. The Elektronika can be programmed though it cannot store a program when turned off.
Nevermind the Casio's ability to solve, integrate, derivate, deal with complex numbers and matrices and more
If you can program the solution on the old Elektronika in the time it takes to solve it on paper, I say you don't need that university anymore.
I did try writing a solver based on the bisection method but didn't get it to work. I should probably try fixing it.
Fortunately our paper exams are only physics and electrical stuff in which the math isn't very involved. Our math exams are digital and we can use MATLAB.