Answer
$$
\left[
\begin{array}{ccc|c}
1 & -3 & 2 & 5 \\
1 & 5 & -5 & 0 \\
3 & 0 & 4 & 7 \\
\end{array}
\right]
$$
Work Step by Step
The row operation $\frac{1}{2}R_1$ means we have to multiply the entire first row of the augmented matrix by $\frac{1}{2}$. The matrix becomes$$
\left[
\begin{array}{ccc|c}
1 & -3 & 2 & 5 \\
1 & 5 & -5 & 0 \\
3 & 0 & 4 & 7 \\
\end{array}
\right]
$$.
