For any normal linear equation of this form, you would typically have one solution for x. For example, if A=3 and B=2, 3x+3=2--->x=-1/3. More generally:
AX=B-A
X=(B-A)/A
This is valid for all real values of A and B EXCEPT when A=0, because we cannot divide by zero.
For example, if A=0 and B=2 we have 0x+0=2. The left side is always zero no matter what x is, so there are no solutions. Suppose A=0 and B=0, we have 0x+0=0. In this case the equation is always true regardless of the value of x, so there are infinitely many solutions.
Statement 1: If we know A is not zero, X=(B-A)/A is a valid solution. Whatever values B and A have, (B-A)/A will have exactly one value, regardless of whether B is zero or not. SUFFICIENT.
Statement 2: If we know B is not zero, there may be one, zero, or infinitely many solutions as outlined above, depending on whether or not A is zero. INSUFFICENT.
ANS: A
