How do you solve \[12+3x=30\] ?

Hint: Now we are given with a linear equation in one variable. Now to solve the equation we will separate the constants and the variables. Now we will simplify the equation and divide the equation with a coefficient of x. Hence we will get the solution of the equation.

Complete step by step solution:
Now we are given with a linear equation in x.
Let us first understand the concept of linear equations.
In linear equations we have variables of degree 1 and constants. When we say the degree of a variable is 1 we mean that the power of the variable is always 1. Now variables are unknown quantities in an equation. Hence we want to find the value of the variable for which the equation holds.
Now consider the given equation \[12+3x=30\]
Now to solve the equation we will first separate the variables and the constants.
Hence we will transpose 12 to RHS of the equation.
Hence we get, $3x=30-12$
Now on simplifying the above equation we get, $3x=18$
Now dividing the whole equation by coefficient of x which is 3 we get,
$\begin{align}
  & \Rightarrow x=\dfrac{18}{3} \\
 & \Rightarrow x=6 \\
\end{align}$
Hence the value of x is 6. Hence the solution of the given equation is x = 6.

Note:
Now note that if mixed fractions are present in the linear equation then first convert them into fractions and then by multiplying the equation by LCM of denominators convert the fractions into integers to ease the calculations. Also if there are square roots in the equation, simplify the equation by taking square on both sides and eliminating square root.