The equation can still be solved but it should be stated clearly at what value of would the equation be undefined. For instance, you have an expression,
1/x+2
When x is equal to -2, the denominator will be 0 resulting to an undefined solution. The value of x here can be any real number except -2.
The answers are B , D , and F
In system A, the first equation multiply by 4
8x - 4y = 12 (1st)
3x + 4y = 10 (2nd)
--------------------add
11x = 22
So answer is B.