P(7,6), Q(1,6), R(4,2)
We have PQ parallel to the x axis. We'll call that the base,
b = 7 - 1 = 6
The altitude is then the y difference h = 6 - 2 = 4
The area is 
Answer: 12 square units
In general we can use the shoelace formula for the area of any polygon given coordinates. We write the points like this:
(7,6), (1,6), (4,2)
(1,6), (4,2), (7,6)
The area is then half the absolute value of the sum of the cross products:

Simplifying this, we get:
(x+4)(x-4) = 0
Now, to get 0, we can replace x for one of these things to make 0, so:
x can either be 4, or -4
Answer:
4/7x - 5 ________________________________________
I want to say that shows a decreasing interval, since it is going downwards.
Area of the large semicircle





Area of the small semicircle





Area of the figure

