0
-3
x2 / y = (6)2 /2 = 36/2 = 18
x/y = 5/(y^2) and y/x = 5/(x^2). So x/y + y/x = 5/(y^2) + 5/(x^2), which equals 5x^2/(x^2 y^2) + 5y^2/(x^2 y^2) equals 5(x^2 + y^2)/25 equals (x^2 + y^2)/5. x^2 = 25/y^2, so you get (25/y^2 + y^4/y^2)/5 equals ((25 + y^4)/y^2)/25, which shows that your math teacher is on crack. Seriously, I'm not sure that's true.
-4
Y/2
y equals 2
Half correct because x = 2 and y = 6
2
-1
If [ y = x + 2 ], then x is not -1 when y = 5.If [ y = x + 2 ],then when x = -1, y = 1,and when y = 5, x = 3.
If: 3x+y = 4 and x+y = 0 Then: x = 2 and y = -2