3x + 4x - 3 = 81
Combine like terms on the left side of the equation. The like terms are 3x and 4x because they contain the same variable x. Add them together then rewrite the equation.
7x - 3 = 81
Add 3 to both sides of the equation to isolate the variable x on one side of the equation.
7x = 84
Divide both sides of the equation by 7 to solve for x.
[tex] \boxed{x=12} [/tex] is your answer.
