Solved Means Alone
Part of the Fundamentals section of Coddy's Algebra journey. Lesson 4 of 64.
An equation is solved when the unknown is alone on one side. Everything else is on the other side. The equation x = 6 is solved, and so is 6 = x. You can swap the two sides of an equation at any time, because "6 equals x" and "x equals 6" mean the same thing. Most people prefer the letter on the left, so swap the sides when the letter ends up on the right.
Take 4 = x - 2. The unknown has 2 subtracted from it, so add 2 to both sides:
4 + 2 = x - 2 + 2
6 = x
The equation is now solved. Swap the sides to write it the usual way round: x = 6. Check the answer by substituting it into the original equation: 4 = 6 - 2 is true.
Challenge
EasySolve the equation 9 = x - 3 for x.
Try it yourself
Solve for x
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Fundamentals
1What an Equation Is
The EquationFinding the UnknownThe Same to Both SidesSolved Means AloneRecap: First Equations4Two-Step Equations
Two Layers to UndoSubtract, Then DivideAdd, Then DivideA Division InsideNegatives in Two StepsRecap: Two-Step Equations2One-Step Equations
Undoing AdditionUndoing SubtractionUndoing MultiplicationUndoing DivisionInverse OperationsRecap: One-Step Equations5Tidying First
Like TermsTerms and Numbers MixedThe Distributive PropertyDistributing a SubtractionTidy, Then SolveRecap: Tidying First