Matrix addition and scalar multiplication

Sum.
$$A+B = \begin{pmatrix} 1+0 & 2-1 \\ 3+2 & 4+5 \end{pmatrix} = \begin{pmatrix} 1 & 1 \\ 5 & 9 \end{pmatrix}.$$

Scalar multiple.
$$3A = \begin{pmatrix} 3 & 6 \\ 9 & 12 \end{pmatrix}.$$

Linear combination.
$$2A = \begin{pmatrix} 2 & 4 \\ 6 & 8 \end{pmatrix}, \qquad 3B = \begin{pmatrix} 0 & -3 \\ 6 & 15 \end{pmatrix},$$
so
$$2A - 3B = \begin{pmatrix} 2 & 7 \\ 0 & -7 \end{pmatrix}.$$