You can see all the trading pairs for Bitcoin here:
https://coinmarketcap.com/currencies/bitcoin/#marketsHowever, if an exchange has a "lower price" than another, it's probably artificially created by:
-A problem or a delay with the exchange's fiat deposits or BTC withdrawals.
-High spread between the buy and sell prices.
-High exchange fees.
Anything outside of that gets arbitraged to death very quickly.