Let's pick a variable to solve for. In this case, a good pick would be y. The reason behind this is we can cancel out the x's easily.
2x + 7y = -1
4x - 3y = -19
Multiple the entire equal by 2. In order to keep the top equation true, we must multiple the entire equation.
2(2x + 7y) = -1(2) => 4x + 14y = -2
Now subtract.
4x + 14y = -2
4x - 3y = -19
0x + 17y = 17
0x is basically 0.
17y = 17
Simply divide each side by 17.
17y / 17 = 17 / 17
y = 1
Now substitute it back into one of equations to solve for x. I'll pick 2x + 7y = -1
2x + 7(1) = -1 ; Start
2x + 7 = -1 ; Multiply 1 by 7
2x = -1 - 7 ; Subtract each side by 7
2x = -8 ; -1 - 7 is equal to -8
x = -4 ; Divide both sides by 2