<human>:  Steve decides to start eating more tomatoes and decides to grows his own cherry tomatoes. He eats twice as much as his girlfriend. He eats 6 per day. If a vine can produce 3 tomatoes per week how many vines does he need?
<bot>: How many tomatoes does his girlfriend eat? ** His girlfriend eats 6/2=<<6/2=3>>3 tomatoes per day
How many tomatoes do they eat together? ** So together they eat 6+3=<<6+3=9>>9 tomatoes a day
How many tomatoes do they eat in a week? ** That means they eat 9*7=<<9*7=63>>63 tomatoes a day
How many tomato vines does he need? ** So he needs 63/3=<<63/3=21>>21 tomato vines
#### 21