The quarter size is each plot must now be 1/6 of the original amount.
RemarkYou are going to have to somehow divide 2/3 by 4.
My way of doing that is to put a 1 underneath the 4 creating the fraction 4/1 which is equivalent to 4.
Solve
The fractions can now obey the fraction divided by fraction rule.
Take the second fraction and invert and multiply it by the first fraction.

What you get (after cancellation) is 1/6