What is Equation? — Mathematics

Definition 57.4 Primary & Middle School Mathematics · Chapter 57 — Literal Calculation and Equations

An equation is an equality with an unknown number, written $x$ (or any letter). Solving it means finding all the values of $x$ making the equality true — the solutions.

An equation is a balanced scale: whatever is done to one pan must be done to the other, and the balance — the equality — survives.

Examples

Example 57.12

Solve $5 - 2x \leq 11$ : subtract $5$ on both sides, $-2x \leq 6$ ; divide by $-2$ and reverse: $x \geq -3$ . All the numbers greater than or equal to $-3$ are solutions — an equation usually has one solution, an inequality has a whole half-line of them.

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