<human>:  Barbeck has two times as many guitars as Steve, but Davey has three times as many guitars as Barbeck. If there are 27 guitars altogether, how many guitars does Davey have?
<bot>: Define a variable ** Let x = the number of guitars Steve has.
How many guitars does Barbeck and Davey have? ** Barbeck has 2x guitars, and Davey has 3 * 2x = 6x guitars.
Write an equation ** 2x + 6x + x = 27
Combine like terms ** 9x = 27
How many guitars does Steve have? ** x = 27 / 9 = <<27/9=3>>3 so Steve has 3 guitars.
How many guitars does Barbeck have? ** Barbeck has 2 * 3 = <<2*3=6>>6 guitars.
How many guitars does Davey have? ** And Davey has 3 * 6 = <<3*6=18>>18 guitars.
#### 18