jmc

Use the area formula $\frac{1}{2}(\text{base})(\text{height})$ with $AB$ as the base to find the area of triangle $ABC$. We find $AB=7-(-3)=10$ by subtracting the $x$-coordinates of $A$ and $B$. Let $D$ be the foot of the perpendicular line drawn from $C$ to line $AB$. We find a height of $CD=1-(-3)=4$ by subtracting the $y$-coordinates of $C$ and $D$. The area of the triangle is $\frac{1}{2}(10)(4)=\boxed{20\text{ square units}}$.