Apparently none of us are correct, I just checked with WA https://www.wolframalpha.com/input/?i=w%2Bx%2By+%3D+-2++w%2Bx%2Bz+%3D+-4++w%2By%2Bz+%3D+19++x%2By%2Bz+%3D+12%2C, and then https://www.wolframalpha.com/input/?i=%28228%2F49*+-48%2F49%29+%2B+%28408%2F49+*+156%2F7%29. The answer is $\frac{434592}{2401}$
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