If Allie want to divide garden into 8 EQUAL rows which in total can be 60, to get the max number of plant in each row we have to divide 60 by 8.
60:8 = 7.5
It says that if Allie puts 7 plants in raw it will be ok, but 8 is too much. (because 60:8 is more than 7 and less than 8). The anwer is 7 plants in row.