I really need a lot of help with this question. Answer step by step and well and explain every conclusion you've got.

Obs : The answer is 60°, but, i need to understand, if possible, why this is the value

Step-by-step explanation:

In a normal triangle, there is a formula as following:

+) cosine of an angle =

Angel B = 30° has:

+) 2 adjacent sides: BC and AB

+) Opposite side: AC

=> We have:

cosine ∠B =

=> cosine 30°  =

=>

=> 2 x (28 - AC^2) = 48

=> AC^2 = 4

We have:

=>

According the inverse Pythagorean theorem, ABC is the right angle triangle with Angle ACB = 90°

=> X + 30 = 90

=> X = 60°

picture below