A painter leans a 25 foot ladder against the wall. The bottom of the ladder is 15 feet from the base of the wall. The painter then moves the bottom of the ladder 8 feet closer to the wall. Much higher is the top of the ladder on the wall

Solving for height of wall (first condition) $$ =\sqrt{25^2-15^2}=20 $$ Solving for the new height:$$ =\sqrt{25^2-7^2}=24 $$ hence the ladder is now 4ft. higher than the wall