Your first step when subtracting integers is (d) subtract the numbers
<h3>How to determine the first step?</h3>
The operation is given as:
Subtraction operation
Assume that the operation is a simple expression that involves subtraction, such as:
a - b
The first step is to subtract the numbers
Hence, your first step when subtracting integers is (d) subtract the numbers
Read more about subtraction at:
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No "x" can not be repeated, a function has one x-element and one y-element
        
                    
             
        
        
        
Answer:
a) 279 b)254
Step-by-step explanation:
Mean = 269 days
standard deviation = 8 days
let n be the pregnancy lenght.  
using normal distribution formula
z = (n – mean)/ standard deviation
n = z * standard deviation + mean
Now, z values for the top 12% has to be found using a z table.
The top 12% means 88% of area under the curve. In this case z = 1,176
n = 1,176 * 8 + 269
n = 278.4 = 279
The bottom 3% means 97% of area under the curve. In this case z = -1,882
n = -1,882 * 8 + 269
n = 253.94 = 254