The shaded area is the repeated identity.

Based on the ratio, we can treat the Square's area as 3 units. But 3 is not exactly divisible by 5. So we multiply the ratio by 5

3 : 4 = 15 : 20

So we can say that the area of the square is 15 units, and the area of the rectangle is 20 units.

Now we know 1/5 of the square is shaded.

15 x 1/5 = 3.

Or

15 units ÷ 5 = 3 units


So 3 units are shaded.

Unshaded part of square = 15 units - 3 units = 12 units

Total area of figure
= Rectangle + unshaded part of Square
= 20 units + 12 units
= 32 units

Unshaded area = total area - shaded area
= 32 units - 3 units
= 29 units

So 29/32 of the figure is unhaded.