EUR, since it is the stronger of the two currencies.
Because the U.S. dollar is regarded as the central currency of the market, it is always treated as the base currency in any quote where it is one of the pairs. Incidentally, the U.S. Dollar is involved in nearly 90% of all transactions.
In this example, your "pair" of currencies are the Japanese Yen (JPY) and the Euro (EUR). The quote, JPY/EUR= 175.10, means that one Japanese Yen is equal to 175.10 Euros. The currency to the left of the / (JPY in this case) is referred to as base currency and its value is 1. The currency to the right of the / (EUR in this case) is referred to as the counter currency. In this example, one JPY can buy 175.10 EUR, since it is the stronger of the two currencies.
The goal of any trading system is to profit from foreign currency movements. This requires adequate training in basic principles, such as performing a Technical Analysis, using charts and Stop/Loss tools, and keeping up-to-date with economic and political events. In a sense, training never ends.
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