The inverse of an operation is the operation which gets you back to the number you started with.
For example, if you start with the number , and then add :
To get back to the , you have to subtract from .
Therefore addition and subtraction are inverse operations.
Similarly, division is the inverse of multiplication, and vice versa:
The case of exponents and logarithms is slightly more complicated, since neither operation is commutative. After raising a number to a power, you can use the logarithm to get back to the exponent (not the base.)