The first one is the answer.
        
             
        
        
        
Answer:
A population is defined as the data set which consists of all members of a specified group and the sample contains a part or a subset of a population. 
For example : all the students of a school are population. But out of all, how many students play sports is a sample.
Hence, the answer is - A population is the complete group under study. A sample is the sub-collection of members of the population from which data are actually collected.
 
        
             
        
        
        
Answer:
61
Step-by-step explanation:
A + B = 90
6 - 5x + 7 - 2x = 90
13 - 7x = 90
- 7x = 90 - 13
- 7x = 77
- x = 77 / 7
x = - 11
A: 6 - (5 * - 11) = 6 + 55 = 61
B: 7 - (2 * -11)  = 7 + 22 = 29
Together they equal 90 as they should. 
 
        
             
        
        
        
8
is the answer because8 times 8 equal 69