SO we need 5 numbers that equal to 20, with 5 being the middle number, and ones being the most used number so
1 1 5 x y
According to this, x and y must equal 13 and both be bigger then 5. Because we can rule out every other number, x and y must be 6 and 7.
Your 5 numbers are 1, 1, 5, 6, 7.