You have the following matrices:
A = 1 -1
2 -1
B = 2 -1
-1 8
C = 3 0
-2 1
1. A + B to sum matrices you sum element by element, jus as follow:
A + B = (1+2) (-1 -1) = 3 -2
(2-1) (-1 -8) 1 -9
2. 2B - A multiply matrix B by 2 and then you subtract matrix A:
2B - A = 2(1) 2(-1) - 1 -1 = (2-1) (-2-(-1)) = 1 -1
2(-1) 2(8) 2 -1 (-2-2) (16 -(-1)) -4 17
3. 3C multiply each element of C by 3:
3C = 3(3) 3(0) = 9 0
3(-2) 3(1) -6 3
4. AC you the mulitplication of matrices rule
AC = (1(3) + (-1)(-2)) (1(0) -1(1)) = 5 -1
(2(3) - 1(-2)) (2(0)-1(1)) 8 -1