To be a code breaker, you need to be able to decipher. That means working out what the symbols in a line of code stand for and what they mean.
The figures in the boxes on the left hand side of the page have been given letter codes that describe certain aspects of their appearance. Using this information you can find the code for the shape in the box on the right. There is a detailed explanation of how they work in the example question and answer, so just work out the codes of two figures which have something in common first, and then the rest will fall into place.
If you think about it, you use codes all the time. Every time you send a text you include messages like 'tb' (text back) and 'lol' (come on, you know it!) so doing code breaker quizzes shouldn't be that difficult!
You should be getting the hang of these 11-Plus Non-Verbal Reasoning quizzes by now - hopefully enough to enjoy 'Code Breaker' quiz number 4. Have fun!