To solve this problem, we use the formula:
z = (x – u) / s
where z is the z score value which can be obtained from
the tables, x is the sample value, u is the mean = 6.3 min, and s is the std
dev = 2.2 min
 
at P value = 0.90, the z = 1.28, finding for x:
x = z s + u
x = 1.28 * 2.2 + 6.3
x = 9.116
 
at P value = 1.0, the z = 3.49, finding for x:
x = z s + u
x = 3.49 * 2.2 + 6.3
x = 13.978 ~ 14
 
Therefore the longest 10% calls last about 9.1 minutes to
14 minutes
 
        
             
        
        
        
The ratio of Isabella’s money to Shane’s money is 3:11
Isabella has $33.   
We can make a proportion to solve for how much money Shane has.   
A proportion is two ratios that are set equal to each other.  
Let’s call Shane’s money ‘S’   
We get this proportion:   3/11 = 33/x   
If we cross multiply we get:   
(33) * (11) = (3) * (x)   
Simplifying it, we get:
363 = (3) * (x)   
Divide both sides by 3, we get:
x = 121   
However, the question asks how much money they have together. 
Isabella + Shane = Total
33 + 121 = $154   
<span>They have $154 together.</span>
        
             
        
        
        
180=2x+y
180-y=2x
(180-y)/2=x
        
             
        
        
        
Answer:
$ 78.78
Step-by-step explanation:
Calculate 15% of 68.50. then add it to the total bill. 
 
        
                    
             
        
        
        
Answer:
$18.24 (C)
Step-by-step explanation:
15.20 x 0.20 = 3.04
3.04 + 15.20 = 18.24
Hope this helped!