Given,
Perimeter of semi-circle = 72 m
Width of path around it = 3.5 m
Perimeter of semi-circle = πr + 2r
= \(\frac{22}7\) r +2r = 72
= 22r + 14r = 72 × 7
r = \(\frac{72\times7}{36}\) = 14 cm
Radius including the width of path(R) = r+3.5 = 14 + 3.5 = 17.5 m
So,
area of path = \(\frac{πR^2}2\) - \(\frac{πr^2}2\)