*C.  This can be
% done without inv(D) in one of two ways: SLASH or BACKSLASH (MRDIVIDE or
% MLDIVIDE to be precise).
%
% inv(A)*B and A\B are mathematically equivalent, as are B*inv(A) and B/A,
% so these three methods give the same results (ignoring computational
% errors, which are worse for inv(D)).  Only the first equation looks like
% the equation in your textbook, however.

A = rand (200) ; B = rand (200) ; C = rand (200) ; D = rand (200) ;

tic ; S1 = A - B*inv(D)*C ; toc ;
tic ; S2 = A - B*(D\C) ; 