<human>:  Sam and Drew have a combined age of 54. Sam is half of Drew's age. How old is Sam?
<bot>: Define a variable ** Let x be Drew's age.
How old is Sam, in terms of x? ** Sam is (1/2)x
Set up an equation ** x+(1/2)x=54
Combine like terms ** (3/2)x=54
Multiply by 2 ** 3x=108
Divide by 3 ** x=<<36=36>>36
How old is Sam? ** Sam is 36/2=<<36/2=18>>18 years old
#### 18