The sum of 5 consecutive even numbers is 100. what is the first number in this sequence?

Consecutive numbers are 1 apart.
Consecutive even numbers are 2 apart.
If x is the smallest of 5 consecutive even numbers, then the next 4 consecutive even numbers are x + 2, x + 4, x + 6, and x + 8.

Add all 5 numbers and set equal to 100.
Then solve for x, the smallest of the 5 numbers.

x + x + 2 + x + 4 + x + 6 + x + 8 = 100

5x + 20 = 100

5x = 80

x = 16

The first number is 16.