According to the information given in the exercise: About 47 million people (of a total of 74 million people) in the age group 21-24, have some college experience but no college degree.
Let be "x" the percent of the people in the age group 21-24 that have some college experience but have not earned a college degree.
Analyzing the information provided, you can identify that 74 million people in the age group 21-24 is the 100%. Then, you can set up the following proportion:

Now you can solve for "x":

Therefore, the answer is: 63.5%