How do you solve $ - 6 = 9\left( {x + 8} \right) + 3x $ ?

Hint: In this question, we are provided with a linear equation with $ x $ as a variable. We have to find the value of this variable $ x $ . For such questions, try to shift the variables to one side and the constants to the other side. it would make the question easier.

Complete step by step solution:
In the question, $ x $ is the variable and we have to find the value of this variable.
Reviving the common definitions: constant is the value which remains unaltered or unchanged or mathematically it’s a number itself whereas a variable is the value which can be changed mathematically represented by alphabets or symbols.
 $ - 6 = 9\left( {x + 8} \right) + 3x $
Multiply the numbers inside the brackets in order to remove them.
 $ - 6 = 9x + 72 + 3x $
Take the variables to the left-hand side and the constants to the right-hand sign.
 $ 9x + 3x = - 6 - 72 $
Keep in mind, on changing the directions. Signs will change. Do the basic calculations
 $ 12x = - 78 $
Dividing by $ 12 $
 $ \Rightarrow x = \dfrac{{ - 78}}{{12}} = - 6.5 $ $ $
So, the final answer is $ x = - 6.5 $
So, the correct answer is “ $ x = - 6.5 $ ”.

Note: A linear equation in one variable is an equation that can be written in the form ax b c + = , where a, b, and c are real numbers and . Linear equations are also first-degree equations because the exponent on the variable is understood to be 1