[tex] - 1 < \frac{7x + 12}{9} < 6 | \times 9 \\ - 9 < 7x + 12 < 54 | - 12 \\ - 21 < 7x < 42 | \div 7 \\ - 3 < x < 6[/tex]
[tex]\it -1<\dfrac{7x+12}{9}<6\Big|_{\cdot9}\ \Rightarrow\ -9<7x+12<54|_{-12} \Rightarrow -21<7x<42|_{:7} \Rightarrow \\ \\ \\ \Rightarrow -3< x<6 \Rightarrow A=(-3,\ \ 6)[/tex]
