You see 3 units for the square in the first ratio and 4 units for the square in the second ratio.

This is a repeated identity. Make their units the same by changing the ratio.

The lowest common multiple of 3 and 4 is 12 (3 x 4 = 12, 4 x 3 = 12)


Shaded area to square

= 2 : 3
↓ (multiply by 4)
= 8 : 12

Square to rectangle

= 4 : 7
↓ (multiply by 3)
= 12 : 21

Combined ratio is :

Shaded area to square to rectangle

= 8 : 12 : 21

Area of figure

= Area of square + area of rectangle - overlap (equal to shaded area)

= 12 units + 21 units - 8 units
= 25 units

Fraction of figure that is shaded

= shaded area / area of figure

= 3 units / 25 units

= 3/25