[tex]x - 7 < 2[/tex]
Add 7 to both sides to get x alone in the side.
[tex]x - 7 + 7 < 2 + 7 \\ = x < 9[/tex]
The second example:
[tex]2x + 1 < 9[/tex]
Subtract 1 to both sides
[tex]2x + 1 - 1 < 9 - 1 \\ = 2x < 8[/tex]
Last step divide by 2 for both sides
[tex]x < 4[/tex]
