Answer
Draw a line connecting U and T, and draw a line connecting V and S. Shade the area between those lines.
Work Step by Step
We need to draw lines to make this plane clear. After that, we shade the area between those lines. The edges of this plane are $\overline{UT}, \overline{UV}, \overline{VS}, $ and $\overline{TS}$. Because the lines contain the three given points, we know that the plane includes these points as well.
