(A) What fraction of the triangle is shaded?

(B) What fraction of the square is shaded?

(A) The marks on the two sides show that the joining points are midpoints.

So, the small top triangle is similar to the whole triangle with scale factor: $\frac{1}{2}$.

Hence its area is: $\left(\frac{1}{2}\right)^2 = \frac{1}{4}$

Area scale factor $= \left(\frac{1}{2}\right)^2 = \frac{1}{4}$

The lower unshaded triangle also has the same height ratio $\frac{1}{2}$, so its area is also: $\frac{1}{4}$

Therefore, shaded area $= 1 - \frac{1}{4} - \frac{1}{4} = \frac{1}{2}$.

Shaded fraction $= \frac{1}{2}$.

(B) The marks show each vertex of the shaded quadrilateral joins the midpoints of the sides of the square.

Joining the midpoints of a square forms another square whose area is half of the original square.

Area of midpoint square = $\frac{1}{2} \times$ Area of original square

Shaded fraction $= \frac{1}{2}$.