13, each term is the sum of two preceding ones.
I think it’s D but not completely sure!

Refer to the attachment for step by step explaination.
Answer:
10
Step-by-step explanation:

4 x 5 = 20
= 10
Answer:
x = 8
Step-by-step explanation:
Using the sine or cosine ratio in the right triangle and the exact value
sin30° =
, then
sin30° =
=
=
( cross- multiply )
x = 8