Answer:
Step-by-step explanation:
Given that the random variable X is normally distributed, with
mean = 50 and standard deviation = 7.
Then we have z= 
Using this and normal table we find that
a) 
b) When z=0.02
we get

c) 90th percentile z value =1.645
90th percentile of X 
You just have to combine like terms here
6+7n^3 is the final answer
3 (4x + 6) = 21
4x + 6 = 21/3
4x + 6 = 7
4x = 7 - 6
4x = 1
x = 1/4
8 because it goes from 1s 10s 100s so 8 is the answer