↝ A single coordinate point must make both equations true in order for the point to be a solution.
Substitute x = 3 and y = -4 in both equations.
![3-4=1\\-1=1](https://img.qammunity.org/2021/formulas/mathematics/high-school/psy3x6cxekywdqyw7otrm3ojhqo7usbk0w.png)
The equation isn't true. Therefore, this isn't the solution for the system.
![-6(3)-3(-4)=-3\\-18+12=-3\\-6=-3](https://img.qammunity.org/2021/formulas/mathematics/high-school/bd0h7qpp5rywznyqeg91ic5ylferiny8pi.png)
The equation isn't true for this one.
Conclusion ↝ The (3,-4) isn't the solution.