If you’re talking about the side lengths then the third side is either a number less than 43 OR a number less than 17
The 43 is if it’s the hypotenuse and the 17 is if it’s one of the other sides
If you’re talking about angles, then all of the angles should equal 180 degrees so 30 + 13 = 43 . 180 - 43 = 137 degrees