Problem
What are the dimensions of the matrix \( A = \begin{pmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9 \\ 10 & 11 & 12 \end{pmatrix} \)?
Solution
Step 1 ：The number of rows of matrix A is 4.
Step 2 ：The number of columns of matrix A is 3.
