Question 121358
Let the width of the path be x

New dimension will be:

30-2x and 20-2x

Area is 400

(30-2x)(20-2x)=400

Expand to get 4x2-100x+200=0

Divide by 4 throught the equation to get

x2-25x+50=0

Factorize or use quadratic formula get the value of X.