1) It says he pours an equal amount into the first 7 beakers after pouring 16mL into the 8th so 70/7 = 10mL per beaker for the first 7.
2) If students rotate through 3 activites, each for 8 minutes, 3*8 = 24 minutes total. If it starts at 11:15, 24 minutes after that would be 11:39 (this represents the time they stop). If lunch starts at 12, there will be 21 minutes between the end of gym activities and the beginning of lunch.