We want to subtract the second matrix from the first matrix. The steps are shown below
The rows are horizontal while the columns are vertical
d11(Term in row1 and column 1) = - 2
d12(Term in row1 and column 2) = - 1
d13(Term in row1 and column 3) = 4
d21(Term in row2 and column 1) = - 2
d22(Term in row2 and column 2) = - 10
d31(Term in row 3 and column 1) = - 2