Data Sufficiency (DS) | Re: 10y + 17z = ?

For all DS problems note exactly what the question is asking for, in this case 10y + 17z, and search proactively for the fastest route to exactly that value.

(1) includes three variables and cannot be manipulated to isolate 10y + 17z.

(2) also includes three variables that cannot be manipulated to isolate 10y + 17z.

When there are simultaneous equations visually stack them on your scratch worksheet as such:

x + 2y + 7z = 40
2x
...

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