$\begin{equation*} \begin{cases} x - 4 < 8 &\\ 2x + 5 < 13 &\\ 3 - x > 1 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} x < 8 + 4 &\\ 2x < 13 - 5 &\\ -x > 1 - 3 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} x < 12 &\\ 2x < 8 &\\ -x > -2 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} x < 12 &\\ x < 4 &\\ x < 2 & \end{cases} \end{equation*}$
x < 2
x ∈ (−∞;2)

$\begin{equation*} \begin{cases} 2x - 1 < x + 3 &\\ 5x - 1 > 6 - 2x &\\ x - 5 < 0 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} 2x - x < 3 + 1 &\\ 5x + 2x > 6 + 1 &\\ x < 5 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} x < 4 &\\ 7x > 7 &\\ x < 5 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} x < 4 &\\ x > 1 &\\ x < 5 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} x < 4 &\\ x > 1 & \end{cases} \end{equation*}$
1 < x < 4
x ∈ (1;4)