the shaded part is 36cm^2, so you need to divide it with how many units you get from the ratio. square unshaded to shaded is 5:3, oval unshaded to shaded is 3:2. You know that the shaded part is overlapping, so they are the same. you have to change the ratio so that the unshaded has a common 6. your new ratio is 10:6:9. 36cm^2 = 6units. 1unit=6cm^2. 10+6+9=25. 25×6=150cm^2