Question

What 2 numbers whose sum is 105.7 the numbers are 19, 85.2, 533, 571, 88.2, 525, 20, 17.5, 400, 261, 20.5 ,125, 7, 23, 901, 30

Answer 1

To make it quickly we can consider only those numbers which will give us a decimal of xxx.7. There are only a few numbers like this: 85.2, 88.2, 20.5.
 
I tried adding 85.2 to 17.5 and it gave me 102.5 - it was close but not close enough :)

So I picked 85.2 + 20.5 = 105.7 and voila :)