Original length =150m
Original breadth = 120m Area = 150×120
= 18000m2
Let the width of foot parts be x.
New length = 150+2x New breadth = 120+2x
New Area = (150+2x)(120+2x)
Given, (150+2x) (120+2x) = 2800+18000
18000+240x+300x+4x2 = 2800+18000
4x2+540x−2800=0
x2+135x−700=0
(x+140)(x-5)=0
x=5, -140
x=5m