\[\begin{align}(a+b)+c&=a+(b+c) \\(a\cdot b)\cdot c&=a\cdot(b\cdot c)\end{align}\]
Associativity applies to both addition and multiplication and says that the result of addition or multiplication is the same regardless of the grouping of terms, e.g., \((1+2)+3\) is the same as \(1+(2+3)\) and, similarly, \((1\times2)\times3\) is the
same as \(1\times(2\times3)\).
Subtraction and division are not associative.
