What it is saying is that a brick is a cube, and has sides one match long.
So a single brick requires 12 matches.
If you put two bricks together, they can share matches: one needs 12, the other needs 4 less.
For three or more bricks, each end needs 12 matches, and each non-end brick needs only 4.
So what you have to do is write a function that takes a number of bricks N and returns the number of matches needed to make it: 12 for N == 1, 12 + 8 for N == 2, and 12 + 4 * (N-2) + 12 for values of N greater than 2.
Give it a try: it's not a complex problem. If you are having problems getting started at all, then this may help:
How to Write Code to Solve a Problem, A Beginner's Guide[
^]