Answer: 14.6 feet
Step-by-step explanation:
Since, here a ladder which has the length 15 foot and it is far from the base of the wall by 3.5 feet.
Here L represents the length of the ladder while d represents the distance of the ladder from the base of the wall. ( shown in figure)
While h represents height that the ladder reaches up the wall.
Thus, L= 15 foot, d= 3.5 foot
Then on applying Pythagoras theorem,

⇒
⇒
⇒
⇒
≈ 14.6 foot
Thus,height that the ladder reaches up the wall= 14.6 foot ( approx)