There is a rectangular Garden whose length and width are 60m X 20m.There is a walkway of uniform width around garden. Area of walkway is 516m^2. Find width of walkway

let the width of rectangle be x so the length & breath is increased by 2x so new total area along with walkway is (60+2x)*(20+2x) so (60+2x)*(20+2x)-60*20=516 =>(60+2x)*(20+2x)=1716 =>(30+x)*(10+x)=429=33*13 =>x=3