Let A = $\begin{bmatrix} 5-x & x+1 \\ 2 & 4 \end{bmatrix}$ It is given that the matrix A is singular, therefore |A| = 0 ⇒ $\begin{vmatrix} 5-x & x+1 \\ 2 & 4 \end{vmatrix}$ = 0 ⇒ 4(5 – x) – 2(x + 1) = 0 ⇒ 20 – 4x – 2x – 2 = 0 ⇒ -6x + 18 = 0 ⇒ x = $\frac{-18}{-6}$ = 3 Thus, when x = 3, the given matrix A is singular.