Answer:
25% probability that all three residents will choose the same plumbe
Step-by-step explanation:
For each resident, there are only two possible outcomes. Either they choose the first plumbe, or they choose the second. The plumbers are chosen independent of each other. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
Each resident randomly chooses one of the two plumbers.
This means that 
Three residents:
This means that 
What is the probability that all three residents will choose the same plumb
This is P(X = 0)(all choose the second pumble) or P(X = 3)(all choose the first pumble). So

25% probability that all three residents will choose the same plumbe
Answer:
254/324 which is about 78.4%
Step-by-step explanation:
found area of entire square to be 18² or 324
found area of 4-quarter circles - which equals one circle with radius of 9
A = 81π which is about 70
subtracted 324 and 70 to get 254
ratio of shaded to unshaded is 254 : 324
I believe you set them equal to each other.
2x+4=5x-9
x=4.3
2(4.3)+4=12.6
I think the answer is 12.6