$2017$ goats

The table above show us some indirectly and directly proportional quantities, that can be interpreted as: How much more days, more field of grass eaten, that can be eaten by less goats. So we have the equation:

${10 \over x} = {10 \over 2017} \times {2017 \over 10}$

${10 \over x} = {1}$

$x = 10$

The answer is $10$ days.

A lot of people would have said 2017 days. Good thing I didn't!

One goat is placed in every grass of $1$ square and the goats eat their own part at the same time. So every goat eat the grass area of $1$ time field with $10$ days. So if $2017$ goats eat grass area $2017$ times the field is $10$ days.