They tell us that at first they had 7/8 of a pitcher full of lemonade, and they ask us to know what fraction is left if they have taken 1/2 of the pitcher of lemonade for a while, which means that it would be a subtraction between what had at the beginning and what they have taken, would be:
7/8 - 1/2 = (14 - 8) / 8 * 2 = 6/16 = 3/8
Which means that 3/8 of the pitcher of lemonade remains.
