Answer:
1) [tex]x+2x\leq 18[/tex].
2) [tex]6[/tex] years
Step-by-step explanation:
Let Hanna's sister be [tex]x[/tex] years old.
Then Hanna will be [tex]2x[/tex] years old.
The sum of their ages will be [tex]x+2x[/tex] years.
The statement "no more than 18" means the sum of their ages is less than or equal to 18.
The required inequality is;
[tex]x+2x\leq 18[/tex].
2)
The inequality we just found is
[tex]x+2x\leq18[/tex].
We simplify to get;
[tex]3x\leq 18[/tex].
we divide both sides by [tex]3[/tex] to get;
[tex]x\leq 6[/tex].
Therefore the oldest age Hannah's sister can be is [tex]6[/tex] years