Answer:
In order for three numbers to form a triangle, the sum of any of the two numbers must be greater than the third number. In this case, 12+20>24, 20+24>12, and 12+24>20. Therefore, this is a triangle.
c^2_a^2+b^2
24^2_12^2+20^2
576_144+400
576_544
576>544
This is an obtuse triangle, as c^2>a^2+b^2.
Explanation: