I see a lot of advice going around about why students have trouble solving math problems. It's always easier to blame the crime on the victim. So, here is my advice, and it's very simple. If you are a student not in college yet, and you don't understand some math concept or have trouble solving the problems - well, it's the teacher's fault, not yours. The solution: find a better teacher!
I know my advice will offend a lot of people because there are a lot of bad teachers out there, especially in Mathematics. Many teachers below University level think that because they've studied teaching methods, and got some teaching credential, they don't need to understand Mathematical concepts. They teach Mathematics as a set of rules. And when the rules don't work they simply give up.
Mathematics is not a right-answer game. Mathematics is a form of art, just as much as painting or photography. But many teachers try to teach it as a set of rules for how you do things. For example, 2+2 can be 4 or 1 or 0 or whatever you like - depending on the context -because you can define your own mathematics - and that's what mathematics is about.
Play Mathematics like you play an interactive game on the computer; there are many ways to get to the next level, not just one. Find a teacher who who understands what Mathematics is about and makes mathematics fun and creative and I guarantee you will be successful!