# subtraction

Subtraction like addition, is associative – that is, a series of subtractions can be carried out in any order. Starting with a piece of wood 10 units long [A], we can cut off first 2 units and then remove a further 3 units from the 8 remaining (so completing the sum 10 - 2 - 3 = 5). Or [B] we can remove first 3 units and then cut off another 2 units from the original 10. This time the subtraction sum is 10 - 3 - 2 = 5 but the result is exactly the same.

Subtraction is the binary operation of finding
the difference between two quantities or numbers; it is the inverse of addition.
The difference of two numbers, *a* - *b*, is the number that
has to be added to *b* to give *a*. *a* is called the **minuend** and *b* the **subtrahend**.
Subtraction can also be seen as the solution of an equation since the difference
(*a - b*) may be expressed as *b* + *x* = *a*.
The subtraction of negative numbers is equivalent to addition, since *a* - (-*b*) = *a* + *b*.