Question 1136349
How high up a vertical wall will a {{{26}}}-foot-long extension ladder reach if its {{{base}}} is placed {{{10}}} feet away from the wall? 

here you have right triangle where extension ladder represents hypotenuse,  {{{base}}} and a vertical wall height  represent legs

use Pythagoras theorem:

{{{hight^2=26^2-10^2}}}

{{{hight^2=676-100}}}

{{{hight^2=576}}}

{{{hight=sqrt(576)}}}

{{{hight=24}}}

-> extension ladder reach hight of {{{24}}} ft  up a vertical wall

so, answer is: B. {{{24}}} feet