let's write it as fractions:
\(\frac{2}{5} \frac{5}{7} \frac{1}{2}\)
we can simplify whatever is both in the nominator and the denominator: so fist, 5:
\(\frac{2}{1} \frac{1}{7} \frac{1}{2}\)
\(\frac{2}{7}\frac{1}{2}\)
now, 2:
\(\frac{1}{7}\frac{1}{1}\)
so:
\(\frac{1}{7}\)
this is the answer!
