Presumably you understand Cramer's rule. What is it about applying it that you need help with? To get you started, one of the steps you need to perform is to replace various entire columns in A with the column vector B. Suppose for example you are at the third column. You would do it like this:
C = A;
C(:,k) = B;
where k is equal to 3. You can do this as part of a for-loop with k increasing from 1 up to 5. You will also need matlab's 'det' function for finding the determinant of a square matrix.
