Find whether the following matrix is singular or non singular ?

$\left[\begin{array}{ccc}3& 5& 7\\ -2& 1& 4\\ 3& 2& 5\end{array}\right]$

Find whether the following matrix is singular or non singular ?

$\left[\begin{array}{cc}7& 5\\ -4& 7\end{array}\right]$

Find $k$ if the following matrix is singular

$\left[\begin{array}{cc}7& 3\\ -2& \mathrm{k}\end{array}\right]$

Find k if the following matrix is singular

$\left[\begin{array}{ccc}4& 3& 1\\ 7& \mathrm{k}& 1\\ 10& 9& 1\end{array}\right]$

Find $\mathrm{k}$ if the following matrix is singular

$\left[\begin{array}{ccc}\mathrm{k}-1& 2& 3\\ 3& 1& 2\\ 1& -2& 4\end{array}\right]$

If $\mathrm{A}=\left[\begin{array}{ccc}5& 1& -1\\ 3& 2& 0\end{array}\right] , \mathrm{Find} ({\mathrm{A}}^{\mathrm{T}}{)}^{\mathrm{T}}.$

$\mathrm{If} \mathrm{A}=\left[\begin{array}{ccc}7& 3& 1\\ -2& -4& 1\\ 5& 9& 1\end{array}\right] , \mathrm{Find} ({\mathrm{A}}^{\mathrm{T}}{)}^{\mathrm{T}}.$

 Find $a,b,c$ if$\left[\begin{array}{ccc}1& \frac{3}{5}& a\\ b& -5& -7\\ -4& c& 0\end{array}\right]$  is a symmetric matrix.