Math question :D

This week Tuesday, it was the problem solving day where we can eat while we solve math problems during class. Sheets were handed out and everyone started to solve the problems given. There were three sections to the sheet, Part A, Part B, and Part C.

Part A was very easy and i could just do it myself, but Part B, it became somewhat challenging. Part C, I did try to solve one but it was really challenging and I did not have enough time to solve them D:
Anyways, while I was going through the sheet, I really liked question number 15 and I really did enjoy solving it. Here is the question:
Four points are on a line segment as shown. If AB:BC= 1:2 BC:CD= 8:5 and find the ratio of AB:BD.

This question seems quite confusing at first but when you look at it carefully, it's quite easy. So this is how I solved it. AB and BC is 1:2 meaning half of one another. BC and CD is 8:5 ratio. Both of these ratios include BC, except in different numbers. So one ratio says BC is 2 and other side says it's 8.

AB is half of BC meaning 8/2 = 4. So we can find out AB is 4. The question left to solve is, what is BD? To find BD, all you have to do is add BC and CD together: 8+5= 13.
What is AB:BD? We found out what AB is 4 and BD is 13. So the ratio would be 4:13

It wasn't so hard was it? I mean I did find it confusing at first but when you read it several times, information that has been given to you would seem more clear and understandable.