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