Answer
$W$ is not a subspace of $R^2$.
Work Step by Step
Let $W$ be a subset of $V$ such that
$W=\{(x, y) : x-y=1\}, \quad V=R^{2}.$
It is easy to see that $(0,0)\not\in W$ since $0-0=0\neq1$.
Hence, $W$ is not a subspace of $R^2$.
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