A rectangular park 60 m long and 40 m wide has two concrete crossroads running in the middle of the park and rest of the park had been used as a lawn. If the area of the lawn is 2109 m² then the width of the road is

Let width = x m

Area of Park = 60 × 40 = 2400 m²
Area of lawn = 2109 m²
So, the area of mid way path = 2400 - 2109 = 291
Area of mid way path = x($$l$$ + b - x)
x(60 + 40 - x) = 291
x(100 - x) = 291
Now you can choose from option or solve in detail.
x² - 100x + 291 = 0
x² - (97 + 3)x + 291 = 0
x² - 97x - 3x + 291 = 0
x(x - 97) - 3(x - 97) = 0
(x - 3)(x - 97) = 0
If x - 3 = 0
x = 3 m