Isolate the variable, arranging the terms of x on one side of the equation and all
the plain numbers on the other side of the equation. USE INVERSE PROPERTIES OF REAL NUMBERS and
the PROPERTIES OF EQUALITY.
Additive Inverse of +4, Addition Prop of Eqlty
Computations, simplifications
Additive Inverse of +12x, Addition Prop of Eqlty
Add terms of x, Commutative Property of Equality
Computation
Multiplicative Inverse of -9, Multiplication Prop of Eqlty
Simplifications, having used multiplicative inverse
The solution process should be straightforward, and in practice, can be done in fewer steps.
Use the solution found for x to check in the original equation to see if it works.