Answer:
The mean = 17.54 
Step-by-step explanation:
Form a table as below;
<u>Interval         Frequency{f}      Midpoint of frequency{x}          fx    </u>
1-7                    19                         4                                            76
8-10                  14                         9                                            126
11-15                  15                         13                                           195
16-20                20                        18                                           360
21-35                 10                        28                                          280
36-50                13                         43                                          559
Sum                   91                                                                        1596
The mean  of grouped data = Sum of { Interval Midpoint * Frequency } /Sum of frequency 
The mean= 1596 / 91
The mean = 17.54 
 
        
             
        
        
        
We can then write an equation representing this problem as:
e−1.5mi=5.25mi
Now, add 1.5mi to each side of the equation to solve for e while keeping the equation balanced:
e−1.5mi+1.5mi=5.25mi+1.5mi
e−0=6.75mi
e=6.75mi
The plane's starting elevation was 6.75 miles 
Hope this helps!
 
        
             
        
        
        
Answer:
1. D
2. x=65
Step-by-step explanation:
Hi!
Your answer is D because 78 is 120% of x
120% in decimal point is 1.2.
So it's 1.2x is the same as 120% of x
For question 8:
1.2x=78
Isolate x by divide 1.2 on both sides
78/1.2=65
 
        
             
        
        
        
Since 20 min is 1/3 of a mile 20 min*3=1 hour. then u multiply 2/5 by 3 to get 6/5.