Answer:
The first one (circle split into 4), 5th one (rectangle split into 10), and last one (right triangle split into 2)
Explanation:
You can do this by counting the amount of sections each shape is split into, then seeing if the amount of shaded in parts is equal to the empty parts. If so, then half is shaded. There are exceptions, though, like the 4th image of a triangle. The top section is smaller and thinner than the bottom, making it not exactly 1/2. However the last triangle is 1/2 because both sections are equal.
Hope this helps!