You'll find it easier to understand if you illustrate the problem as what is shown in the attached picture. From the illustration and the problem description, two equations can be formulated:
HJ = 2JK
HJ + JK = HK
2JK + JK = 78
3JK = 78
JK = 78/3
JK = 26
Answer:
a) P(X<50)=0.9827
b) P(X>47)=0.4321
c) P(-1.5<z<1.5)=0.8664
Step-by-step explanation:
We will calculate the probability based on a random sample of one moped out of the population, normally distributed with mean 46.7 and standard deviation 1.75.
a) This means we have to calculate P(x<50).
We will calculate the z-score and then calculate the probability accordign to the standard normal distribution:

b) We have to calculatee P(x>47).
We will calculate the z-score and then calculate the probability accordign to the standard normal distribution:

c) If the value differs 1.5 standard deviations from the mean value, we have a z-score of z=1.5

So the probability that maximum speed differs from the mean value by at most 1.5 standard deviations is P(-1.5<z<1.5):

you could use this equation to help you solve it;
x + (x + 42) = 138
the first step is to combine like terms;
2x = 138 -42
2x = 96
X = 96/2
X = 48
we already solved for x now substitute it in the equation I gave you.
48 + (48 + 42) = 138
48 + 90 = 138
hope it helped...if you have any concerns just let me know:)