Question 763074
Given field, perimeter = 180+240=420 yards.  Area = 12600 sq.yds.

Wanted x and y, {{{2(x+y)=420}}} and {{{xy>12600}}}


Solve the equation either for x or y, and substitute this into the inequality.  Solve the resulting inequality.  You might want to repeat the method starting with the other variable from the equation.