Answer: Junior is 3 3/10 feet tall . 
Explanation:
As given 
 Junior's brother is 5 1/2 feet tall
 i.e 
 Junior's brother is 11/2 feet tall
Junior is 3/5 of his brother's height
 Thus 
 Junior's heights = 3/5 times his brother's height
 Putting all the values in the formula 
Junior's Height = 3/5 X 11/2
 Junior's height = 33/10
 Junior's height = 3 3/10 feet 
 Therefore Junior is 3 3/10 feet tall .