This is seemingly very simple, but I cannot think of anything wrong with it. https://onlinegdb.com/Mc9ni9Qmf
in lines 325 - 636 of algebra.h. when you go through the menu, choose do_algebra, then 1_variable, then equation, then enter 15 + 45 = x, or any other operator. follow the directions, and it will output x=0. 15 + 45 is not 0. I have isolated that something is wrong when setting al_1_solution at the end of each operation module, using debug. the datatypes line up, both are long double. I have tried everything I could think of. Also, another module of my calculator, the detect_simple_operation, uses the same concept, yet it works fine. this is puzzling. (located in functions.h @ lines 96 - 250).
If someone could help me that would be great, I am self taught at c++, so I might have missed something critical...