This is classic statistical analysis which involves histograms, and whether data skews left, right etc, based on whether the data clusters either at head or tail of data's shape.

Trick here is to look at days student earned that amount. The days represent the frequency of an observation. usually the amount earned which has the most days or frequency is where the median lies. In this case 84$ has 7 days where that amount was earned. The median is just the middle term...so the probability of the middle term being on the amount earned which had the most days would be highest.

cheers,

sd

there are 20 students in total. so the money spent by the 10th and the 11th student will give you the median.
the amount spent are
$96 , $84 , $80 , $70, $48 arranged in descending order.
Now if you count, both the 10 and 11th student in increasing or decreasing order have spent 84$
so median is 84+84/2=84