Anne has worn a black shirt on 6 of the last 20 days. Considering this
data, how many times would you expect Anne to wear a black shirt in the
next 10 days?
Considering she wore a black shirt 6 times in 20 days will give you the statistic of 3/10. If the question is about the next 10 days then she will wear 3 black shirts. (It's also 1/2 of the original question.)