Human: Timothy has three times the number of pens that George owns. Sarah has half as many pens as Timothy. If George has 18 pens, how many pens does Sarah have? Assistant: 
How many pens does Timothy have? ** Timothy has 18 * 3 = <<18*3=54>>54 pens.
How many pens does Sarah have? ** This means that Sarah has 54 /2 = <<54/2=27>>27 pens.
#### 27