Question 664922
draw a right triangle that has one leg of 12 and another leg of (18-13). The hypotenuse of that triangle will be the distance between the two chimney tops.

{{{c^2 = 12^2 + 5^2}}}
{{{c^2 = 144 + 25}}}
{{{c^2 = 169}}}
{{{c = 13}}}

The distance from chimney tops to chimney top is 13 feet.