Working backwards:
17-3=14
14/2=7
7 is the second term in the sequence. Continue backwards.
7-3=4
4/2=2
2 is the first term in the sequence, aka your answer.
Answer: There are 7,677 streets named as " First Street" and 7, 189 streets named as "Main Street" .
Step-by-step explanation:
Let x be the number of streets named as First Street .
y be the number of streets named as Main Street.
AS per the given information, we have the following system of equations :

Substitute the value of x from (2) in (1) , we get

Put value of y in (2), we get

Hence , there are 7,677 streets named as " First Street" and 7, 189 streets named as "Main Street" .
If it is not an integer, it would have to be a decimal.
To evaluate the probability that the lifespan will be between 1440 and 1465 hours will be given by:
P(1440<x<1465)
using the z-score formula we obtain:
z=(x-μ)/σ
where:
μ=1450
σ=8.5
hence
when x=1440
z=(1440-1450)/8.5
z=-1.18
P(z<-1.18)=0.1190
when x=1465
z=(1465-1450)/8.5
z=1.77
P(z<1.77)=0.9625
hence:
P(1440<x<1465)
=0.9625-0.1180
=0.8445