Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
John buys 2 shirts. The first shirt costs $6 more than the second shirt. If the first shirt costs $15, how much, in dollars, did the shirts cost in total?

### Response:
The second shirt is 15-6=<<15-6=9>>9 dollars.
Both shirts cost 15+9=<<15+9=24>>24 dollars.
#### 24