The system of equations of two unknowns is formulated and solved.
The fraction that satisfies the request is 
, since in 
the negative signs are canceled and the first fraction is obtained.
For #6;
We know that there are 46% male students and 30% of them are seniors. This means that we have to assume that 30% of the male students are seniors and that 30% of the female students are seniors. Taking 30% of 46% gives us 13.8%.
For #7;
We are looking for the possibility that we choose a junior student (22%) or a sophomore student (28%). This adds up to 50% (22%+28% = 50%). That is out answer.
(x-1)(x-1) + (y+2)(y+2) = 3
x2 -1x -1x + 1 + y2 +2y +2y +4=3
x2 +y2 -2x +4y + 2=0
A is the answer
