bagaimana cara menyelesaikan soal matriks diatas?

-1  d       4  -5       3c  1-a
          +           =
-b  3      -3  b       -5c  3a-1

3       d-5              3c  1-a
                      = 
-b-3  3+b             -5c  3a-1


------------------------------------
3 = 3c
c = 1
-----------------------------------
-b-3 = -5c
-b-3= -5(1)
-b = -2
b = 2
--------------------------------
3+b = 3a-1
3+2 = 3a-1
6 = 3a
a = 2
---------------------------------
d-5 = 1-a
d-5 = 1-2
d = 4
-------------------------

maka a+b+c+d = 2+2+1+4 = 9