Answer:
4
Step-by-step explanation:
BCD is a right triangle. The Pythagorean Theorem applies; a^2 + b^2 = c^2, with c being the hypotenuse. a^2 + 9 = 25, so a^2 = 16, so a = 4
The answer is 105. If you look at the pattern, sequence 2 goes up in 15. 75 + 15 + 15 = 105.
