Which ratio is equivalent to 30:20 all that apply

The random variable x is the number of occurrences of an event over an interval of ten minutes. it can be assumed that the probability of an occurrence is the same in any two-time periods of an equal length. it is known that the mean number of occurrences in ten minutes is 5.3. the appropriate probability distribution for the random variable

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9

700 miles the train takes 5 hours to a travel the distance at what unit rate is the train traveling?