Explanation:
1. first multiply -1 times all elements of matrix A
2. then multiply 1/3 by all elements of matrix B
3. then add each corresponding entries to get the result.
from step 1. matrix A will be
-4 -2. -1. -3
-2. 0. 1. -3
step 2. matrix B will be
3. -1. -2. -4
3. -10. 10. -1
add each corresponding elements to get
-1. -3. -3. -7
1. -10 11. -4