Answer: 7 glasses 
Explanation:
Hi, to answer this question, first, we have to subtract the amount of juice poured (1/8) to the amount of remaining juice before he poured some (1). 
1-1/8 = 7/8 remaining juice 
Since he pours the same amount into more glasses until the pitcher is empty, we have to divide the remaining juice (7/8) by the amount poured in each glass (1/8). 
7/8 ÷ 1/8 = 7 glasses 
Feel free to ask for more if needed or if you did not understand something.