No, it isn't a right triangle.
The fourth choice - 5/104.
In one cube, there are 3 even numbers - 2,4,6. For two cubes, the total probability is 36.
3*3 / 36 = 9/36
For letters, there are five vowels over 26 letters = 5 / 26
Multiply the two probabilities to get the probability of rolling two even numbers and selecting one of the vowels.
9/36 * 5/26 = 5/104
There are a couple of ways to tackle this one, using the 45-45-90 rule or just using the pythagorean theore, let's use the pythagorean theorem.
the angle at A is 45°, and its opposite side is BC, the angle at C is 45° as well, and its opposite side is AB, well, the angles are the same, thus BC = AB.
hmmm le'ts call hmmm ohh hmmm say z, thus BC = AB = z.