No, each triangle is not a right triangle
For this case we can use the following trigonometric relationship to solve the problem:

Where,
C.O: opposite leg
h: hypotenuse
Substituting values we have:

Clearing x we have:

Making the corresponding calculations we have:
Answer:
The value of x is given by:
(x^2 + 4x + 8)(2x - 1) = 2x(x^2 + 4x + 8) - (x^2 + 4x + 8) = 2x^3 + 8x^2 + 16x - x^2 - 4x - 8 = 2x^3 + 7x^2 + 12x - 8
What is the question? Cual es la pregunta?
Use the left and right triangles. (the two smaller ones -- ACD and BCD)
By similar triangles ACD is similar to BCD
on the left AD/CD is one ratio
On the right CD/DB is the other. These two ratios are equal because they are corresponding parts.
AD / CD = CD / DB
AD = 3
DB = 12
CD = ??
Substitute.
3/CD = CD/12 Cross multiply
36 = CD^2
sqrt(36) = sqrt(CD^2)
CD = 6 <<<<==== Answer.
A <<<<====Answer.