4a + 7b = 38 -> (1)
9a + 7b = 68 -> (2)
Subtract (1) from (2),
9a - 4a + 7b - 7b = 68 - 38
5a = 30
a = 6
we know that
Area of the circle is equal to

where
r is the radius
in this problem



therefore
the answer is the option
d. 113.04 sq. in.
Multiply 8 3/4 lb by the conversion factor 16 oz
------------
1 lb
Then 35 lb 16 oz 560 oz
-------- * ----------- = ------------- = 140 oz (answer)
4 1 lb 4
(3,4) and (-5,6) are "coordinate planes".
These appear in algebra and math when you're graphing. These coordinate planes consist of "x" and "y" (x,y). The x's (which are 3 and -5 in your situation) should be graphed accordingly using the x-axis and the y's (which are 4 and 6 in your situation) should be graph accordingly using the y-axis.