We are given that
In right triangle ABC, if angle A is 90 degrees, angle C is 34 degrees, and AC is 71.4, find BC.
Solution
We will first draw a diagram to illustrate the information
Above we want to find x
The method to use is SOHCAH
From the right angle triangle above we have above, we have the adjacent side and we want to find the hypotenus, so we use cosine
i.e

We need to solve for x here

Thus, |BC| = 86.1 (to the nearest tenth
You can again ignore the parenthesis because you are not distributing anything.
Your equation will look like this
3x + 11 + 6x
You can move each of these numbers around any way you like. You can combine the 3x and the 6x if you want, but they did not do that. You cannot take the x away and put it in front of the 11 though.
B. is your answer. All they did was move the 6x inside the parenthesis and the 11 out of the parenthesis.
Always remember, when you are adding things together, the parenthesis don't matter!
The answer is A. If you divide 3/8 which equals .375. Then you multiply .375 by 6 to get 2.25!
:D Hope this helps!