Having seen the solution on the integral math site, my contradictions don't line up with theirs, but I assume that there are multiple ways it could be done.
For part (i) Forming inequalities for all numbers then expanding the brackets you obtain $ab-abc>\frac{4}{27}$ , $ac-abc>\frac{4}{27}$ and $bc-abc>\frac{4}{27}$
If you subtract any one of the inequalities from the other you obtain something of the form $a(b-c)>0$ which without loss of generality, can apply for any permutation of a, b and c.