Answer
33
Work Step by Step
Step 1. See graph, sketch the triangle with the given vertices.
Step 2. Recall the determinant formula for the area of a triangle:
$\begin{array}( \\A=\pm\frac{1}{2} \\ \\ \end{array}
\begin{vmatrix}-2&5&1\\7&2&1\\3&-4&1 \end{vmatrix}$
Step 3. Evaluate the determinant (column1 expansion for this case)
$A=\frac{1}{2} |(1)(-7(4)-2(3))-(1)(-2(-4)-5(3))+(1)(-2(2)-5(7))|=33$
