$3 \times\left[\begin{array}{ccc}7 & 5 & -10 \\ 3 & 8 & 0\end{array}\right]$

Full solution

3 \times\left[\begin{array}{ccc}7 & 5 & -10 \\ 3 & 8 & 0\end{array}\right]

Understand Operation: Understand the operation to be performed. $\newline$ We need to multiply each element of the matrix by the scalar value $3$ .
Multiply First Row Element: Multiply the first element of the first row by $3$ . $\newline$ $3 \times 7 = 21$
Multiply Second Row Element: Multiply the second element of the first row by $3$ . $\newline$ $3 \times 5 = 15$
Multiply Third Row Element: Multiply the third element of the first row by $3$ . $\newline$ $3 \times (-10) = -30$
Multiply Third Row Element: Multiply the third element of the first row by $3$ . $\newline$ $3 \times (-10) = -30$ Multiply the first element of the second row by $3$ . $\newline$ $3 \times 3 = 9$
Multiply Third Row Element: Multiply the third element of the first row by $3$ . $\newline$ $3 \times (-10) = -30$ Multiply the first element of the second row by $3$ . $\newline$ $3 \times 3 = 9$ Multiply the second element of the second row by $3$ . $\newline$ $3 \times 8 = 24$
Multiply Third Row Element: Multiply the third element of the first row by $3$ . $\newline$ $3 \times (-10) = -30$ Multiply the first element of the second row by $3$ . $\newline$ $3 \times 3 = 9$ Multiply the second element of the second row by $3$ . $\newline$ $3 \times 8 = 24$ Multiply the third element of the second row by $3$ . $\newline$ $3 \times 0 = 0$