Equations are made up of two expressions on either side of an equals sign, such as:

\[x + 1 = 2\]

To solve an equation, you aim to find the value of the missing number.

'I think of a number, add four, and the answer is seven.'

Written algebraically, this statement is \(x + 4 = 7\), where \(x\) represents the number you thought of.

\(x + 4 = 7\) is an example of an **algebraic equation** where \(x\) represents the unknown number.

The number you first thought of must be three (\(3 + 4 = 7\)). Therefore, \(x = 3\) is the solution to the equation \(x + 4 = 7\).