1. 用代入法解方程组$\begin{cases}y = 2x - 3,①\\3x - 2y = 8②\end{cases}$时，将方程①代入②中，所得的方程正确的是( )

A.$3x + 4x - 6 = 8$
B.$3x - 4x + 6 = 8$
C.$3x + 2x - 3 = 8$
D.$3x - 2x - 6 = 8$

2. 用代入法解方程组$\begin{cases}3x + 4y = 2,①\\2x - y = 5②\end{cases}$时，比较合理的变形是( )

A.由①，得$x = \dfrac{2 - 4y}{3}$
B.由①，得$y = \dfrac{2 - 3x}{4}$
C.由②，得$x = \dfrac{5 + y}{2}$
D.由②，得$y = 2x - 5$

3. 用代入法解下列方程组：
(1)$\begin{cases}m = 3 - n,\\2m - 3n = 1;\end{cases}$
(2)$\begin{cases}2a + b = 3,\\b = 2a - 1;\end{cases}$
(3)$\begin{cases}x + y = 17,\\5x + 3y = 75;\end{cases}$
(4)$\begin{cases}2x + y = 1,\\3x - 2y = - 9;\end{cases}$
(5)$\begin{cases}2x + y = 7,\\2x + 4y = 16;\end{cases}$
(6)$\begin{cases}2x + 3y = 5,\\3x - y = 2;\end{cases}$
(7)$\begin{cases}3x + 8y = 5,\\4y = x + 5;\end{cases}$
(8)$\begin{cases}7x + 3y = 5,\\5x + 6y = - 8.\end{cases}$