Answer: The required area of triangle RST is 9 sq. units.
Step-by-step explanation: We are given to find the area of triangle RST shown in the figure.
We know that the AREA of a triangle with base 'b' units and height 'h' units is given by

From the figure, we note that in ΔRST,
base, b = RS = 6 units
and
height, h = UT = 3 units.
Therefore, the area of ΔRST, will be

thus, the required area of triangle RST is 9 sq. units.