The Continents were all joined into one land mass
66,73 73-66=7
13,21 21-13=8
10,20 20-10=10
the missing no. is 9 so
52+9=61.
the pattern is
66,73,13,21,52,61,10,20
Yes, a text file with a .txt extension can be read by Linux/Unix/Mac as they are ASCII unformatted.
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