This is an exponential growth problem. Exponential growth can be expressed mathematically in the following way:

.
Parameter a presents initial amount.
Parameter r is percentage increase.
Parameter t is time.
An equation that would describe given problem is:

t is the time in years.
I attached the graph of this function.
Answer:
85%
Step-by-step explanation:
If 30 of them have their own lawn service then that means 170 of them do not have their own lawn service.
Seeing as there are 200 houses in total, the fraction of people who don't have lawn service is 170/200. This is equal to 0.85 or 85%.
I would say B but I can't see the question very well.
Answer:
6 : 1
Step-by-step explanation:
b - 3a / 9 = a /3
Cross multiply
3(b - 3a) = 9a
Expand
3b - 9a = 9a
Add 9a to both sides
3b = 9a + 9a
3b = 18a
Divide both sides by 3
b = 6a
Ratio of a : b
6 : 1
There was a 20% decrease
48/60 × 100 = 80%
100 - 80 = 20%