In any given right triangle, the Pythagorean Theorem can be used to show that it is a right triangle.
The Pythagorean Theorem is a^2+b^2=c^2. In a right triangle, a and b would be the shorter legs of the triangle, while c would be the hypotenuse.
So for this problem, you would plug in the numbers in the order that they are listed to see if it is a right triangle.
F would be: 2^2+4^2=7^2. In this case, the sides are not equal.
G would be: 6^2+8^2=10^2. In this case, 100=100. So this is a right triangle.
H would be: 4^2+9^2=12^2. The sides are not equal.
J would be: 5^2+10^2=15^2. The sides are not equal.
Your answer would be G, since the sides are equal. Hope this helps! :)