Your matrix X1 X2 X3 b 1 2 3 -4 -4 2 1 -2 2 3 3 1 3 -2 1 Write down the main matrix and find its determinant X1 X2 X3 1 2 3 -4 2 1 -2 2 3 1 3 -2 Δ = -12 Replace the 1st column of the main matrix with the solution vector and find its determinant X1 X2 X3 1 -4 3 -4 2 3 -2 2 3 1 3 -2 Δ1 = -12 Replace the 2nd column of the main matrix with the solution vector and find its determinant X1 X2 X3 1 2 -4 -4 2 1 3 2 3 1 1 -2 Δ2 = -24 Replace the 3rd column of the main matrix with the solution vector and find its determinant X1 X2 X3 1 2 3 -4 2 1 -2 3 3 1 3 1 Δ3 = -36 x1 = Δ1 / Δ = (-12) / (-12) = 1 x2 = Δ2 / Δ = (-24) / (-12) = 2 x3 = Δ3 / Δ = (-36) / (-12) = 3 Solution set: x1 = 1 x2 = 2 x3 = 3