If you have the numbers 3, 5, and 10, to take a normal average, it would be 3+5+10, divided by the total number of data points—in this case 3. For a weighted average, you'd multiply each number by its weight first. For instance, if the first number is twice as important, it would have a weight of 2, while the others would have a weight of 1. In that case, it would be (3x2)+(5x1)+(10x1). Then, divide that by 3.