2x + 3x + 5x = 180
  
10x = 180
  
x = 18
  
2x = 36, 3x = 54, 5x = 90
  
They add up to 180 (definition of sum of angles of a triangle.)
 
        
             
        
        
        
Answer:
3 can 
Step-by-step explanation:
there 
 
        
             
        
        
        
Answer:
We conclude that  a researcher  used simple random sample.
Step-by-step explanation:
We know that select a sample of five children from a class of 30, a researcher puts each child’s name on a slip of paper, then shuffles the papers in a hat and randomly picks five names.  
We conclude that  a researcher  used simple random sample.
Because every children  has an equal chance of being included in the sample.