Ok, no problem. The first step we take is to recognize the fact that the question is naturally split into two parts, so we let the narrow point in the diagram be labeled C.
The number of paths from A to B is (paths from A to C)(paths from C to B), make sure you see why.
With this, we need to find a way to calculate the number of paths from A to C (C to B is easy).
First, we realize that to make a 12 step path, we can only go up and to the right. This means that a path from A to C will go up exactly 3 times and to the right 5 times.
This means that a path from A to C will consist of 8 options, 3 going up and 5 going right. In this, we want to find the number of ways to insert 3 points to move up in an 8 step path (for example, on steps 1, 4, and 5, we move up), and the 5 spots to move right will naturally fill in. To pick 3 points from the 8 step path, there are \(C(8, 3)\) ways, meaning 56 combinations. From C to B, we use the same method and find 6 paths. Therefore, from A to B, there are 56*6 = 336 paths. There are many math competition questions that are like this, for more methods, explanations, and such, search up "number of paths from a to b" or "paths on a grid"
Hopefully, this answered your question, have a great day!