Answer: [tex]337.77\%[/tex]
Step-by-step explanation:
Given
For 70 year old, premium is 79.79 per month
For 80 year old it is 349.30 per month
Percentage increase in premium costs from age 70 to 80 is
[tex]\Rightarrow \%\ \text{increase}=\dfrac{349.30-79.79}{9.79}\times 100\\\\\Rightarrow \%\ \text{increase}=\dfrac{269.51}{79.79}\times 100\\\\\Rightarrow \%\ \text{increase}=337.77\%[/tex]