You can put this solution on YOUR website! AB is the horizontal line , so the altitude from point C is the perpendicular (vertical) line through C, .
The slope of BC is , so the slope of the (perpendicular) altitude from/through A is . The altitude is on the line ---> --->
The intersection of those two altitudes is the intersection of the 3 altitudes, the orthocenter. It's coordinates are and
The orthocenter of triangle ABC is (1,7).