**Example 1: Subtract previous number**

The third number is found by subtracting the second number from the first number. In fact, this is a variation on the fibonacci sequence. For example:

The answer is 12 - - 4 = 12 + 4 = 16

A variation on this is the pattern where the 2nd number is subtracted from the 1st number to find the 3rd number:

The answer is: -24 - 44 = -68

**Tip:** Exceptions of this kind are rare. Usually the exception will be Fibonacci, only look for this pattern if you can't figure it out with the other patterns. You can quickly check almost all exceptions with the first three numbers. Can you build the 3rd number from the 2nd and 1st numbers?