There is NO matrix for "rounding to the nearest integer" and this problem does not ask you to find one. In fact, I see nothing here that requires matrix calculations at all. This is a matter of solving a system of linear equations. Of course, if you are used to using matrices to solve systems of differential equations, go ahead and do so. In (b),set up the matrix problem to solve for the number of people who go to the barber. If the answer doesn't happen to be an integer, round off after solving the matrix equation.