First rewrite into 2 inequalities,
[tex]-2\lt3x+4[/tex]
[tex]3x+4\lt31[/tex]
Solve each of the inequalities,
[tex]-2\lt3x+4\implies3x\gt-6\implies x\gt-2[/tex]
[tex]3x+4\lt31\implies 3x\lt27\implies x\lt9[/tex]
So our x is between -2 and 9 which can be written as,
[tex]-2\lt x\lt9[/tex]
or as an interval,
[tex]x\in(-2,9)[/tex]
Hope this helps :)
