First, you would find the area of the whole square (based on the perimeter of the footpath). Since the footpath is 3 meters wide, you would add two 3 meter lengths to the length of the square plot to find the length of the entire square.
1) 50m + 3m + 3m = 56m length
Multiply 56 by 56, since that is the length of the square, and for the area of the square the formula is A = 2*L
2) 56m * 56m = 3136m squared
Then, find the area of the square plot in the inside.
3) 50m * 50m = 2500m squared
Subtract the two areas to find the area of the foot path going around the square plot.
4) 3136m^2 - 2500m^2 = 636m^2
Answer: the footpath has an area of 636 meters squared