7. The set S of numbers has the following properties：

　　I） If x is in S， then 1/x is in S.

　　II） If both x and y are in S， then so is x + y.

　　Is 3 in S？

　　（1） 1/3 is in S.

　　（2） 1 is in S.

　　Consider （1） alone. Since 1/3 is in S， we know from Property I that 1/（1/3）

　　= 3 is in S. Hence， （1） is sufficient.

　　Consider （2） alone. Since 1 is in S， we know from Property II that 1 + 1 = 2

　　（Note， nothing in Property II prevents x and y from standing for the same n

　　umber. In this case both stand for 1.） is in S. Applying Property II again s

　　hows that 1 + 2 = 3 is in S. Hence， （2） is also sufficient. The answer is D.

　　8. What is the area of the triangle above？

　　（1） a = x， b = 2x， and c = 3x.

　　（2） The side opposite a is 4 and the side opposite b is 3.

　　From （1） we can determine the measures of the angles： a + b + c = x + 2x + 3

　　x = 6x = 180

　　Dividing the last equation by 6 gives： x = 30

　　Hence， a = 30， b = 60， and c = 90. However， different size triangles can hav

　　e these angle measures， as the diagram below illus