「年齢を見分ける」とは日本語でよく言いますが、英語で的確な言葉がわからずtellを使って作文してみました。
It's difficult to tell real someone's age just by looking, especially in case of other country's people.
よろしくお願い申し上げます。
It's hard to guess someone's age just by looking at them, especially foreigners.
It's hard to tell someone's age just by their appearance, especially foreigners.
①It's hard to guess someone's age just by looking at them, especially foreigners.
→見ることだけで年齢を見分けるのが難しい、特に外国人の場合。
②It's hard to tell someone's age just by their appearance, especially foreigners.
→見た目だけで年齢を見分けるのが難しい、特に外国人の場合。
アメリカ合衆国 
