How would I work this out

I'm don't understand how to work out this question. It's on physics and maths tutor A level chemistry question 11 in the Amount of a substance QP.

Heres what I did so pretty much you start from the titration by working out the moles of the sodium thiosulfate then you can just divide by two to get the moles of I2. You can link the first and second equation because the only place where iodine is supplied from is the first equation. Therefore all of the moles that are reacting with the sodium thiosulfate must have came from the first reaction. Once you have the moles of I2, you can see thats its in a 1:1 ratio to ClO- so that lets you get the moles for NaClO. From there work out its mass so we have a 25 cm3 sample from the 100 cm3. We multiply by four to get back to the number of moles in 100 cm3. The reason we can do this is because the 100cm3 comes from the orginal diluted sample so it will still have all the moles from that intial 10cm3 present, just a lower concentration. This is not the same with the 25cm3 sample where it will actually have a lower number of moles. From here we now just take our mass of NaClO and divide it by the mass of the entire bleach solution which we can derive from density* volume. We get the answer to be 4.16%

Thank you so much! Do you have any tips in general for answering these types of questions in the amount of a substance topic?