Answer:
1: 52 minutes
2: 416 links
Step-by-step explanation:
(Supposing that the right numbers are 8, 20 and 13:)
After 20 minutes, Emmanuel had added 8*20 = 160 links
The number of links Emmanuel added in instant 't' is equal to 160+8*t, with t in minutes being the time counted when Allesia started to add links.
The number of links Allesia added in instant 't' is equal to 13*t
To know the moment when they have the same number of links, we just have to make both equations equal:
160 + 8*t = 13*t -> 5*t = 160 -> t = 32 minutes
As Emmanuel started 20 minutes earlier, he worked 52 minutes when Allesia caught up to him.
The number of links he added is 160+8*(32) = 416 links
