Remember that the area of a Triangle is
A = (1/2)(Base)(Height)
You can find the Base of this Triangle by finding the difference in the x coordinates at points R and Q, and you can find the Height of this Triangle by finding the difference in the y coordinates at either points R and P or points Q and P. (The height will be the same either way)
Then you can plug the Base and Height into the Area formula to answer the question.
