BPP Practice and Revision Kit. Question 113 and 118.

I think we must be using different editions of the Revision Kit. I have no 113 or 118 (although I do have a 11.3 and 11.8).

I have found the questions, but I really do not understand what you want from me! The Revision Kit gives the answers and the workings for them, so you are going to have to say which bit of the workings you do not understand.