The answer is 12. 
Steps
If that number is x
(3+x)/(8+x)=3/4
"Cross multply"
4(3+x)=3(8+x)
12+4x=24+3x
x=12
To check: add 12 to 3 and 8. 3+12=15 and 8+12=20. 15/20=3/4
        
             
        
        
        
Answer: 16 men
32 women
38 children
Step-by-step explanation:
Let x represent the number of men in the group.
Let y represent the number if women in the group.
Let z represent the number of children in the group.
A group of 86 people consist of men women and children. This means that 
x + y + z = 86 - - - - - - - - - - - - 1
There are twice as many women than there are men. It means that 
x = y/2
There are 6 more children than there are women. This means that
z = y + 6
Substituting x = y/2 and z = y + 6 into equation 1, it becomes
y/2 + y + y + 6 = 86
 multiplying through by 2, it becomes
y + 2y + 2y + 12 = 172
5y = 172 - 12 = 160
y = 160/5 = 32
x = y/2 = 32/2
x = 16
z = y + 6 = 32 + 6
z = 38
 
        
             
        
        
        
To find the average number of pages the student read from day 2 to day 6, add the total pages in these days and divide by 5 days.
<h3>What is the average?</h3>
This is a very common word used in mathematics and stadistics to refer to the mean value in a set of values.
<h3>How to calculate the average from day 2 to day 6?</h3>
Add the pages the person read these days and then divide by 5 (total of days).
For example:
35 + 45 + 10 +25 + 20 = 135 / 5 = 27 pages
Note: This question is incomplete because the table is missing; due to this, the answer is based on general knowledge.
Learn more about average in: brainly.com/question/2426692