The answer would be 61. First, if you are trying to figure out the pattern. You must subtract the
second number with the first then fourth number with the fifth and so
on, you get.
73 minus 66 equals 7.
21 minus 13 equals 8.
XX minus 52 equals x.
20 minus 10 equals 10.
Basing on the pattern of the set of numbers, x will equal 9, To get this you must do 52 and 9 which will equal 61.
