I'm a 23 years old plumber and looking for some advice to raise my math skills in order to get a better job where I don't have to sweat my ass sore 7-15:30.

I've applied to school once and in the test I found out my math skills were insufficent. Now I'm pretty confident with the trigonometry stuff like law of sines and law of cosines, quadratic equation, boolean algebra (including the usage of karnaugh map), but mostly just basic math you'd learn in high school if you live in USA.

Now comes the question. What should I do next? Where to go from here?