Answer:
D
Step-by-step explanation:
As

because the rate is of
1/8 and
8/8=1
First off 3/9 and 6/9 are already common denominators. In some fractions you would need to find the least common denominator like in a problem like 1/2 + 4/5. Also 3/9 plus 6/9 results in 9/9 and 9/9 equals 1. Most fractions adding it subtracting results in a pan answer as a fraction but in this case it’s a whole number.
The answer is 3 because all you have to do is plug in the answer and then you have to solve the answer and go from there.
Find the z-scores for the two scores in the given interval.

For the score x =391,

.
For the score x = 486,

Now you want the area (proportion of data) under the normal distribution from z = -1 to z = 0. The Empirical Rule says that 68% of the data falls between z = -1 to z = 1. But the curve is symmetrical around the vertical axis at z = 0, so the answer you want is HALF of 68%.
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