$\begin{equation*} \begin{cases} x - 3y = 5 | *3&\\ 3x + 2y = 4 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} 3x - 9y = 15 &\\ 3x + 2y = 4 & \end{cases} \end{equation*}$
3x − 9y − (3x + 2y) = 15 − 4
3x − 9y − 3x − 2y = 11
−11y = 11
y = 11 : (−11)
y = −1
3x + 2y = 4
3x = 4 − 2y
3x = 4 − 2 * (−1)
3x = 4 + 2
3x = 6
x = 6 : 3
x = 2
Ответ: (2;−1)

$\begin{equation*} \begin{cases} 3x + y = 1 | *5&\\ 2x - 5y = -22 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} 15x + 5y = 5 &\\ 2x - 5y = -22 & \end{cases} \end{equation*}$
15x + 5y + 2x − 5y = 5 − 22
17x = −17
x = −17 : 17
x = −1
2x − 5y = −22
5y = 2x + 22
5y = 2 * (−1) + 22
5y = −2 + 22
5y = 20
y = 20 : 5
y = 4
Ответ: (−1;4)

$\begin{equation*} \begin{cases} 2x - 3y = 9 &\\ x + 2y = 1 | *2 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} 2x - 3y = 9 &\\ 2x + 4y = 2 & \end{cases} \end{equation*}$
2x − 3y − (2x + 4y) = 9 − 2
2x − 3y − 2x − 4y = 7
−7y = 7
y = 7 : (−7)
y = −1
2x + 4y = 2
2x = 2 − 4y
2x = 2 − 4 * (−1)
2x = 2 + 4
2x = 6
x = 6 : 2
x = 3
Ответ: (3;−1)

$\begin{equation*} \begin{cases} 5x + y = 24 | *4 &\\ 7x + 4y = 18 & \end{cases} \end{equation*}$
$\begin{equation*} \begin{cases} 20x + 4y = 96 &\\ 7x + 4y = 18 & \end{cases} \end{equation*}$
20x + 4y − (7x + 4y) = 96 − 18
20x − 4y − 7x − 4y = 78
13x = 78
x = 78 : 13
x = 6
7x + 4y = 18
4y = 18 − 7x
4y = 18 − 7 * 6
4y = 18 − 42
4y = −24
y = −24 : 4
y = −6
Ответ: (6;−6)