The matrix A is the coefficient matrix and contains the coefficients of all variables.
The coefficient of equation 1 are mentioned in row 1 and coefficients of equation 2 are mentioned in row 2.
So,
a = 5
c = 7
b = 3
d = -2
So,
a - b + c + d = 5 - 3 + 7 - 2 = 7