Question

What is the sum of all odd integers between 8 and 26

Answer 1

Odd integers between 8 and 26
{ 9,11,13,15,17,19,21,23,25}...added = 153 <==

Answer 2

It's an arythmetic sequence:

$a_1=9;\ d=2;\ a_9=25\\\\S_n=\dfrac{a_1+a_n}{2}\cdot n\\\\S_9=\dfrac{9+25}{2}\cdot9=\dfrac{34}{2}\cdot9=17\cdot9=153\\\\Answer:\boxed{153}$