If vectors $\vec{a}=\hat{i}-2 \hat{j}+\hat{k}, \vec{b}=2 \hat{i}+4 \hat{j}+5 \hat{k}$ and $\vec{c}=\hat{i}+6 \hat{j}+7 \hat{k}$ then find the sum of vectors.
If $x+y=\left[\begin{array}{ll}2 & 1 \\ 1 & 2\end{array}\right]$ and $2 x-y=\left[\begin{array}{ll}1 & 2 \\ 2 & 1\end{array}\right]$ then find the value of $x$.