Usually in college-and-up mathematics, if you get the answer, you know when you have the answer, because you have a correct proof. You don't need the solutions

Usually in college-and-up mathematics, if you get the answer, you know when you have the answer, because you have a correct proof. You don't need the solutions, the whole point is to write your own, which is much more work and which will invariably differ from the official ones -- sometimes slightly, sometimes drastically.