Answer:
[tex]\mathrm{A)\:}-6[/tex]
Step-by-step explanation:
Notice that in the second equation, the coefficient of [tex]y[/tex] is [tex]2[/tex] times greater than in the first. Therefore, by making the coefficient of [tex]x[/tex] in the second equation [tex]2[/tex] times greater than in the first, it's impossible to only isolate one variable.
Therefore, when [tex]a=-3\cdot 2=\fbox{-6}[/tex], there are no solutions to this system.
