Question 1173709
We can use Pythagorean theorem for this type of question.
In the illustration we can see that the ladder, base (length of wall to ladder), and wall make a right angle triangle which we can use the theorem for to find the base.
The Pythagorean theorem is {{{a^2+b^2=c^2}}}
In this case a is the wall, b is the base and c will always be the hypotenuse (the longest side or the side opposite of the right angle). 
We can manipulate the theorem to find the base or b. So we want to find b which we can do by changing {{{a^2+b^2=c^2}}} to {{{b=sqrt(c^2-a^2)}}}. Now we can input the numbers: {{{b=sqrt(28^2-19^2)}}}
b=20.6 ft rounded to the nearest tenth. 
Therefore the wall is 20.6 ft from the ladder at the base.