Answer:
21
Step-by-step explanation:
I think its 21, because the BD line divides the big triangle into 2 ones and they are equilateral triangle, sorry if I'm wrong
BD = 21
The sector divided AC into two equal pieces and since this is a right triangle the height of the triangle BD is equal to half of the base
(21+21) / 2 = x
42 / 2 = x
21 = x
