I don't have any good recommendations. I just upload such one-off requests to AIstudio, ChatGPT and the like. But keep in mind AI isn't perfect at math. They sure make a lot of mistakes with my assignments. I don't know what level your maths test was, AI does an acceptable job at elementary school maths. With higher level maths, it'll give both correct and wrong results by chance. Might be good enough, I don't really know.
I'd recommend Wolfram Alpha. That's not local, nor is it AI. But it solves equations, calculates and transforms and draws graphs with precision and there isn't any guessing involved.