Question 103619
The rectangular field is 200x300 or 60,000 sq.m. currently. 
You want to leave 50,000 sq. m and the area of the road would take up the rest.
Area of old field = Area of new field + Area of the road
60,000 = 50,000 + Area of road
We know the width of the road, x, but which dimension is the length of the road? 
Is it 200m or is it 300m. 
We'll solve for both. 
For the length of the road = 200m.
Area of road = 200*x 
{{{60000=50000+200*x}}}
{{{10000=200x}}}
{{{x=50m}}}
For the length of the road = 300m.
Area of road = 300*x 
{{{60000=50000+300*x}}}
{{{10000=300x}}}
{{{x=33.3m}}}