There are an infinite number of shapes, because a shape can have any number of sides. This is where we get into our laws of fractals. A fractal is a shape with an infinite perimeter and area, meaning that every level of infinity is another shape, but can be beat by another shape. However, this is all philosophical math and goes way beyond the context of your question.
To keep it short and simple, there are an infinite number of shapes in the world.
The interior angles of a triangle must add up to 180 eighty degrees.
Since the ratio is 7:5:3, let's say that the three angles have degrees 7x, 5x, and 3x
7x+5x+3x = 15x = 180
-> x = 12
Therefore, the three angles are 7*12=84, 5*12=60, 3*12=36 degrees.
Changing the order of the denominator doesn’t change the product. 4•6=24 and 6•4=24 again.
