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?
His girlfriend eats 6/2=
<gadget id="calculator">6/2</gadget>
<output>3</output>
3 tomatoes per day.
So together they eat 6+3=
<gadget id="calculator">6+3</gadget>
<output>9</output>
9 tomatoes a day.
That means they eat 9*7=
<gadget id="calculator">9*7</gadget>
<output>63</output>
63 tomatoes a day.
So he needs 63/3=
<gadget id="calculator">63/3</gadget>
<output>21</output>
21 tomato vines.

<result>21</result>