Answer:
The proportion of electric toothbrush prices are between 104.60 dollars and 108.20 dollars is 0.0099
Step-by-step explanation:
A set of electric toothbrush prices are normally distributed with a mean of 87 dollars and a standard deviation of 8 dollars.

Standard deviation = 
We are supposed to find proportion of electric toothbrush prices are between 104.60 dollars and 108.20 dollars i.e.P(104.60<x<108.20)

At x = 104.60

Z= 2.2
At x=108.20

Z= 2.65
Refer the z table for p value :
P(x<108.20)-P(x<104.60)=P(Z<2.65)-P(Z<2.2)=0.9960-0.9861=0.0099
Hence The proportion of electric toothbrush prices are between 104.60 dollars and 108.20 dollars is 0.0099
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8/20 is greater than 2/10. If you were to make the denominators the same, by mulipling 2x2 and 10x2, you would get 4/20, which is less than 8/20.
Bare with me a minute, I am still trying to figure it out. Here is what I have so far.