lets remind ourselves about some rules of adding and substracting matrices
you can add or subtract:
2x3 with a 2x3 matrix
a 3x3 with a 3x3
You can NOT add a 2x3 with a 3x2or a 3x3
first pictures is a 2x4 matrix , 2 represents the number of columns, 4=rows
so 1=d, 2=b, 3=a, 4=c
