The answer is D, i.e. the system was solved via elimination
If you multiply the first equation by 5, the system becomes
[tex] \left \{ {{-5x-10y=35} \atop {5x-6y=-3}} \right. [/tex]
If you sum the two equations, you get
[tex] -16y = 32 [/tex]
And so if you substitute the second equation of system A with this new equation, you'll get system B.
