Verified answer

а)

[tex]3x - y = 9 \\ 2x + y = 11 \\ \\ 2x + 3x + y - y = 9 + 11 \\ 5x = 20 \\ x = 20 \div 5\\ x = 4 \\ \\ 2 \times 4 + y = 11 \\ 8 + y = 11 \\ y = 11 - 8 \\ y = 3[/tex]

Ответ: ( 4 ; 3 )

б)

[tex]3x + 5y = 10 \\ x - 4y = - 8 \: \: | \times ( - 3) \\ \\ 3x + 5y = 10 \\ - 3x + 12y = 24 \\ \\ 3x - 3x + 5y + 12y = 10 + 24 \\ 17y = 34 \\ y = 34 \div 17 \\ y = 2 \\ \\ x - 4 \times 2 = - 8 \\ x - 8 = - 8 \\ x = - 8 + 8 \\ x = 0[/tex]

Ответ: ( 0 ; 2 )