Distributing a Subtraction
Part of the Fundamentals section of Coddy's Math journey. Lesson 26 of 64.
The number outside multiplies every term inside, sign included. 3(x - 4) is 3x - 12, because 3 × (-4) = -12. Forgetting to multiply the second term (writing 3x - 4) is the classic slip.
3(x - 4) = 9
3x - 12 = 9
3x = 21
x = 7
A negative outside flips every sign inside: -2(x - 5) = -2x + 10. Read the outside number with its sign, distribute it to each term, and the arithmetic looks after itself. Check the answer above: 3(7 - 4) = 3 × 3 = 9.
Challenge
Solve the equation 5(x - 2) = 20 for x.
Try it yourself
5(x - 2) = 20
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