The way I would do it is by rounding 8.91 up to 9 and I would round 34,871.081 up to 35,000.
9*35,000=315,000
Hopefully I was able to help in some way.
So this statement is caused for subtracting. So we have to subtract 6,700.00 from 3,995.00 and the answer would be 2705
Hope this helps :)
Solution:
Population in the city= 10,000
As genetic condition affects 8% of the population.
8 % of 10,000

As, it is also given that, there is an error rate of 1% for condition (i.e., 1% false negatives and 1% false positives).
So, 1% false negatives means out of 800 tested who are found affected , means there are chances that 1% who was found affected are not affected at all.
So, 1% of 800 
Also, 1% false positives means out of 10,000 tested,[10,000-800= 9200] who are found not affected , means there are chances that 1% who was found not affected can be affected also.
So, 1% of 9200 
1. Has condition Does not have condition totals = 800
2. Test positive =92
3. Test negative =8
4. Total =800 +92 +8=900
5. Probability (as a percentage) that a person has the condition if he or she tests positive= As 8% are found positive among 10,000 means 9200 are not found affected.But there are chances that out of 9200 , 1% may be affected

that is Probability equal to 0.01 or 1%.