a) Ratio of unshaded part to shaded part of square = 3 : 1 = 6 : 2

Ration of shaded part to unshaded part of rectangle = 2 : 9

Since shaded part of square = shaded part of rectangle,

Unshaded part of square : shaded part : unshaded part of rectangle = 6 : 2 : 9 (ans)

b) 2u -> 36 cm²

1u = 18 cm²

(6+2+9) u = 17u = (17 x 18) cm²  = 306 cm² (ans)