Step-by-step explanation: The letter "x" is often used in algebra to mean a value that is not yet known. It is called a "variable" or sometimes an "unknown". In x + 2 = 7, x is a variable, but we can work out its value if we try!
see the attached figure to better understand the problem
we know that
In the right triangle ABC, the tangent of angle of 30 degrees is equal to divide the opposite side to the angle of 30 degrees (AC) by the adjacent side to the angle of 30 degrees (BC)