Answer:
58.33%.
Step-by-step explanation:
We have been given a data set {1.5, 2.3, 1.7, 3.6, 2.9, 4.2} and we are asked to find the percentile for value 2.9.
First of all let us arrange our data points from smallest to largest as: {1.5, 1.7, 2.3, 2.9, 3.6, 4.2}.    
We can see that our data set has 6 data points and 2.9 is 4th data point.  
We will use percentile rank formula to solve our problem.   
 , where,
, where, 
P= Percentile rank,
i= Rank of the data point,
n = Total number of data points.
Upon substituting our given values we will get, 
 
 

 
 
 
 
 
  
Therefore, percentile rank for the value 2.9 is 58.33%.