a:
Just divide both sides by 7. Since 7 is positive, you don't need to change the inequality sign:
[tex]7j>77\iff j>11\}[/tex]
In set notation, we write
[tex]\{j \in \mathbb{R}\ :\ j>11[/tex]
b:
Subtract 9 from both sides:
[tex]17\leq x+9 \iff 8\leq x[/tex]
In set notation, we write
[tex]\{x \in \mathbb{R}\ :\ x\geq 8\}[/tex]
