Answer: There are approximately 853827 new cases in 6 years.
Step-by-step explanation:
Since we have given that
Initial population = 570000
Rate at which population decreases is given by

Now,
First year =570000
Second year is given by

Third year is given by

so, there is common ratio ,
it becomes geometric progression, as there is exponential decline.
so,

a=570000
common ratio is given by

number of terms = 6
Sum of terms will be given by

We'll put this value in this formula,

So, there are approximately 853827 new cases in 6 years.
the answer is 10:20.
Hint for the future: be sure to write in the full problem. I only knew the answer because I had to do it myself, but people need more context if they are going to help you.
X = 15 , see photo for solutions