Answer:
x= 6
Step-by-step explanation:

You will subtract 10x from 12x and get 2x

Subtract 4 from 16 to get 12

You will then divide both sides by 2
= 
x= 6
The second one is hard to read but since ∠3 is 54° you should just start from there
Hope this helps
Answer:
it is easy use the formula of triangle which is 1/2(base × height) and base is the side where the height touches and height means the perpendicular line.
And in some cases there may be the use of pythagoras theorem
The answer is -- A. Exactly one solution