Question 201481
Because this is a right triangle then:
a^2+b^2=c^2
12^2+x^2=(x+6)^2
144+x^2=x^2+12x+36
12x=144-36
12x=108
x^2=108/12
x=9 ft. ans. for the height of the ladder against the building.
(9+6)=15 ft. ans. for length of the ladder.
Proof:
12^2+9^2=15^2
144+81=225
225=225