Well, we can see that this is a special right triangle, a 30-60-90 triangle, where m angle A = 30, m angle C = 60, and m angle B = 90.
The side lengths are in the ratio 1:sqrt3:2, which in our case is 12:12 x sqrt3:24
12 x sqrt 3 = 20.7846096908 or approx 20.8 as shown in the graph below:
ALERT: Sorry, the top point is meant to be A, the bottom left one B, and the bottom right one C.
We can multiply 12x 20.7846 x 1/2 and get:
124.7076
or approximately
124.71
Answer: 124.71