Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the attendance of the game that has the opponent of The Nationals with a record of 68-51?

### Inputs:
table_name: table, columns: ['Date', 'Opponent', 'Score', 'Loss', 'Attendance', 'Record']

### Response:
SELECT SUM Attendance FROM table WHERE Opponent = nationals AND Record = 68-51