2.3 is smaller than 2.6: we can see it just by looking at the digits from left to right.
now, where does 2\(\frac{4}{5}\) stand?
its fraction part is equal to
\(\frac{4*2}{5*2}= \frac{8}{10}\)
do that means that 2\(\frac{4}{5}\)=2.8
which is bigger than 2.6
so the final order is
2.3 2.6 2\(\frac{4}{5}\)