Question 88262
THE GARDEN IS 30*40=1200 SQFT. WITH THE WALK WAY THE AREA IS 1800.
SO WITH THE WALKWAY WE HAVE THE FOLLOWING DIMENTIONS:
(30+2W)(40+2W)=1800 WHERE THE 2W IS THE WIDTH OF THE TWO WALKWAY ONE ON EITHER WIDTH & LENGTH.
(30+2W)(40+2W)=1800
1200+80W+60W+4W^2=1800
4W^2+140W+1200-1800=0
4W^2+140W-600=0
4(W^2+35W-150)=0 
USING THE QUADRATIC EQUATION WE GET:
W=(-35+-SQRT[35^2-4*1*-150])/2*1
W=(-35+-SQRT1225+600])/2
W=(-35+-SQRT1825)/2
W=(-35+-42.72)/2
W=(-35+42.72)/2
W=7.72/2
W=3.86 FT. ANSWER FOR THE WIDTH OF THE SIDEWALK.