There are 21 cherry tomatoes on the tomato plant.  2 birds eat one-third of the tomatoes.  How many are still left on the tomato plant?
The birds eat this many tomatoes: 21 / 3 = <<21/3=7>>7 tomatoes.
There are this many tomatoes left on the plant: 21 - 7 = <<21-7=14>>14 tomatoes.
#### 14