Answer:
1) [tex]2s+s\leq18[/tex]
2) 6 years old
Step-by-step explanation:
Let Hannah's age be [tex]h[/tex] and her sister's age be [tex]s[/tex]
It means [tex]h=2s[/tex]
It means the sum is LESS THAN or EQUAL TO 18. So we can write:
[tex]h+s\leq18[/tex]
1. We can substitute first equation into second equation to get our desired inequality of the situation. Thus,
[tex]h+s\leq18\\2s+s\leq18[/tex]
2. To find MAXIMUM age of Hannah's sister, let's further simplify the inequality from number 1. So,
[tex]2s+s\leq18\\3s\leq18\\s\leq\frac{18}{3}\\s\leq6[/tex]
Hence, Hannah's sister's age is LESS THAN OR EQUAL TO 6. So maximum age of her sister is 6.