Respuesta :

buttmann65Andrew
I think that the answer is 61 I got this off of google so I'm not 100 percent sure please don't take my word as anything but second advice.
I think the answer is 61 because :
If you split the six numbers into little groups :
66 + 7 = 73
13 + 8 = 21
52 + 9 = 61
10 + 10 = 20
You see the pattern is add one more too each group
Therefore, the answer is 61
:)