So for instance I figured out that numerical methods are a thing that you can use to approximately solve differential equations, which often don't have a nice analytical solution.
Can I solve differential equations? Not anymore. Can I solve one by the end of this week? Definitely.
What you do in college is a bit of intellectual tourism, looking at wide variety of topics briefly. There are natives who depend on the tourists for part of their living, who know every nook and cranny of PDE solvers. But like in the real world we're mostly at home in one place and tourists everywhere else.
The other answer to your question is that you build up an intuition for where the dragons are. The more tourism you do, the more you come to suspect there are other continents in certain places.