Question

The sum of 5 consecutive odd numbers is 135. What is the second number in this sequence?

Answer 1

Any even number is 2n. Therefore, 2n+1 is an odd number. Apply this logic:
(2n+1)+(2n+3)+(2n+5)+(2n+7)+(2n+9)=135
10n+25=135
10n=110
n=11
So the second number in the sequence is 2n+3= 25.

Answer 2

5 consecutive odd numbers : x, x + 2, x + 4, x + 6, x + 8

x + x + 2 + x + 4 + x + 6 + x + 8 = 135.....combine like terms
5x + 20 = 135
5x = 135 - 20
5x = 115
x = 115/5
x = 23

x + 2 = 23 + 2 = 25 <== this is the 2nd one
x + 4 = 23 + 4 = 27
x + 6 = 23 + 6 = 29
x + 8 = 23 + 8 = 31