Answer:
16 cm
Explanation:
4 + 4 + 3 + 5 = 16
The = sign means that B (which is 4 cm) is equal to D (which had no number)
And because it says that B = D (with the squiggly line (or a tilde)) And the L's (which means that the letters represent an angle) All you have to do is add the numbers together, and you get 16.
Sorry if I explained it badly, you at least got the answer.
(And also, if I'm wrong, please tell me.)