1 & 19. I think possibly you've missed something...?
The numbers are 18 and 12
the 2 numbers are pp and caca
10 and 8
18 and 32
18 and 32
They are 10 and 8
30 + 18 = 48 30 - 18 = 12 The two numbers are therefore 30 and 18.
[8] and [10].
11 and 7 Add them and you get 18, subtract them and you get 4.
503 and 521.
There are infinitely many numbers whose difference is 18 . Every number,say n, differs by 18 from n+ 18 and n -18.
There is a very easy way to do this type of thing:Subtract the difference, then half the answer, this gives the smaller number. Add back the difference to get the larger number.In this case 90 - 18 = 72; 72/2 = 36 then 36 + 18 = 54.