How many people were in the room? (Solution)

6

Initially there were 6 people in the room. It doesn’t matter how old they are, but let’s say they were average 10 years old. Anne is 28 years older than the average so she is 38.

6 * 10 + 38 = 98

98/7 = 14 (the new average age, which increased by 4 years)

Now her sister enters (also 38).

98 + 38 = 136

136 / 8 = 17 (the average increased by 3 more years)