The vertices of a triangle are $A(0 ; 3), B(4 ; 0)$, and $C(x ; 5)$. What is the unknown coordinate of point $C$, given that $0<x<4$, and the area of triangle $A B C$ is 8 square units?
The area of the sought triangle is most simply expressed by including it in a rectangle whose sides are parallel to the coordinate axes. The result is $x=\frac{8}{3}$.