Verified answer

1) Б)

[tex]2x + 3y = 12 \\ 2x = 12 - 3y \: \: | \div 2 \\ x = 6 - 1.5y[/tex]

2) Г)

[tex]\left \{ {{4x - 5y = 7} \atop {5x - 4y = 2 }} \right. \\ \\ 5x - 4y = 2 \\ 4y = 5x - 2 \: \: | \div 4\\ y = \frac{5x - 2}{4} [/tex]

3) А)

[tex]\left \{ {{x = 3y + 2} \atop {2x + 3y = 9 }} \right. \\ \\ 2(3y + 2) + 3y = 9[/tex]