Evaluate $3^{15} \mod(7)$

the least non-negative remainder when $3^{17}$ is divided by 7 is :

The set of values of $x$ satisfying $26 \equiv 5 \pmod{x}$ is _______.

Match List I with List II

Choose the correct answer from the options given below:

If $A' = \begin{bmatrix} -2 & 3 \\ 1 & 2 \end{bmatrix}$ and $B = \begin{bmatrix} -1 & 0 \\ 2 & 3 \end{bmatrix}$

then $(3A + 2B)'$ is :

If $\begin{bmatrix} 2x + 3 & y + 1 \\ 2x - z & 3y \end{bmatrix} = \begin{bmatrix} 7 & -2 \\ -4 & -9 \end{bmatrix}$, then matrix $\begin{bmatrix} 3z + 1 & 4 \\ -2 & 4 \end{bmatrix}$ is equal to:

If A is a skew symmetric matrix, then $A^2$ is