The first image is a triangle with 3 sides,
Number inside = 9 = 3^2
Second image is a rectangle with 4 sides,
number inside = 16 = 4^2
Third image is a rectangle with 5 sides,
number inside = 25 = 5^2
Thus, in the given pattern, the number of sides are increasing by 1, and the number inside the shape is the square of the number of the sides the shape will have.
Hence, the next 3 images in the pattern will be:
A hexagon with 6 sides and number inside = 6^2 = 36
then, A heptagon with 6 sides and number inside = 7^2 = 49
A octagon with 6 sides and number inside = 8^2 = 64