###Human: Kate wants to buy a special pen as a gift for her friend. The pen costs $30, and Kate only has money for a third of that amount. How much more money does she need to buy the pen?, ### Assistant: Currently, Kate has only 1/3 * 30 = $10.
That means Kate needs 30 - 10 = $20 more to buy the pen. 
 So the answer is :  20