Fractions

${{5 \over 8} * {1 \over 5}} = {1 \over 8}$

So, $1 \over 8$ of the tractors are in working conditions.

Just as builderboi said!

$\frac{5}{8}\times\frac{1}{5}=\frac{5\times1}{8\times5}=\frac{5}{40} simplify, \frac{1}{8}$