The length and breadth of a rectangular garden are 40m and 25m respectively. There isa footpath of uniform width around the garden in its inside . of the area of the footpath is 126 square metre, what is its width?

Certainly not English -- the units are metric!

To get the width of the path, subtract the inner garden area from the total:

40*25 - (40-2w)(25-2w) = 126