An equation is a statement that two expressions are equal, like 2x + 3 = 11. Solving an equation means finding the value of the variable that makes the statement true.

To solve, use inverse operations to isolate the variable. Whatever you do to one side, you must do to the other side to maintain balance. For 2x + 3 = 11: subtract 3 from both sides to get 2x = 8, then divide both sides by 2 to get x = 4.

Always check your solution by substituting it back into the original equation: 2(4) + 3 = 8 + 3 = 11. ✓

Expressions can be simplified by combining like terms. Like terms have the same variable raised to the same power. For example, 3x + 5x = 8x, but 3x + 5x² cannot be combined because x and x² are different.