Solved Means Alone
Part of the Fundamentals section of Coddy's Math journey. Lesson 4 of 64.
An equation counts as solved when the unknown is alone on one side and everything else is on the other. x = 6 is solved. So is 6 = x: the sides of an equation can be swapped freely, because "6 equals x" and "x equals 6" say the same thing. Most people prefer the letter on the left, so swap the sides whenever it lands on the right.
Take 4 = x - 2. The unknown has a 2 subtracted from it, so add 2 to both sides:
4 + 2 = x - 2 + 2
6 = x
That is already the answer. Swap the sides to write it the usual way round, x = 6, and check by substituting: 4 = 6 - 2 is true.
Challenge
Solve 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