A dealer in Australia quotes A$1.7430-40/$,
A dealer in Paris quotes $0.8610-20/euro.
A dealer in Germany quotes euro 0.6667-76/A$.
What should the German dealer quote to prevent any arbitrage?
Assuming you are asking what the German dealer should quote Euros per USD.
The formula below is how you find the cross ...
The formula below is how you find the cross rates between currencies.