Final answer:
The 5th number is -15.
Step-by-step explanation:
To find the 5th number, we need to first find the sum of all 5 numbers. Let the 5th number be x. The sum of 4 numbers is 45, so we can write an equation: 45 + x = (5 * 12). Solving this equation gives us x = 45 - 60 = -15.
Therefore, the 5th number is -15.
Learn more about Finding the 5th number in a set of given numbers