How to find Inverse of 2x2 Matrix

In general, the inverse of a real number is a number which when multiplied by the given number results in the multiplicative identity, which is 1. In matrices, the inverse of a matrix A (which is denoted by A-1) is a matrix which when multiplied by A gives the identity matrix, I. i.e., AA-1 = A-1A = I. But how to find the inverse of 2x2 matrix?