I was away on the first lesson and apparently we did series. It seems really weird that a series with positive numbers can result in a negative answer that is a fraction. Challenge of Mathematics seems very different from normal maths but its interesting and makes you think outside the box.
If I was asked to choose a topic, I would choose Cryptography because it looks like an interesting topic and it will be fun learning about code breaking etc. However I would also like to study all the other topics because they all look fun.