Solution:

24

For Explanation : check picture solution.

Solution:

47

Explanation:
At first look, it seems pretty easy but on the contrary, it is pretty tricky a question. So let us simplify it by dividing the triangle into three equal triangles (the triangles so formed if outer side is connected to the center of the circle) and then count the number of triangles in each part by taking two or more parts together.

First, let us take the triangles in one part. There are 4 non-overlapping and 3 overlapping triangles.
4 + 3 = 7
7 * 3 = 21

Next, if we take number of triangles by taking two parts together, there are 8 in total.
8 * 3 = 24

Lastly, the number of triangles if all three parts are taken together, there are a total of 2.

21 + 24 + 2 = 47.

Solution:

64

Solution:

13

Solution:

There are 20 triangles.