please show conditions

A man plays a dice game that involves throwing 3 dice at a time. His winnings are directly related to the number of threes recorded. If the die are fair, what is the probability distribution that affects the outcome of each throw? The frequencies of the threes observed in 80 trials are recorded, together with their expected values, in the following table:

Number of threes     Expected Count        Observed Count 

0                                      27                                 30 

1                                     32                                  20

2                                     12                                  19

3                                      9                                    11

(chi square goodness of fit)please show conditions