The solution by the other tutor uses a valid, very formal algebraic method.
There are many other methods that can be used. I personally find that formal algebraic method awkward; I can get an answer with far less work using a less formal method.
Here is how I would solve the problem....
Given: 6 reporters, 24 articles in 2 days.
The new number of reporters is 12, which is double the original number; that means half as much time. So 12 reporters, 24 articles, 1 day.
The new number of articles is 120, which is 5 times the original number; that means 5 times as much time. So 12 reporters, 120 articles, 5 days.
Although I don't usually do it myself, it can be helpful to make a chart of the given information and of the changes you make to get to the answer:
reporters articles days
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6 24 2 given
12 24 1 twice as many workers, so the time is cut in half
12 120 5 5 times as many articles, so the time is multiplied by 5