In a certain code language, 'he knows spanish' is coded as 'ty fr op' and 'spanish is difficult' is coded as 'fr hg df'. How will 'spanish' be coded in that language?

Let's compare the two sentences and their corresponding codes:
'he knows spanish' → 'ty fr op'

'spanish is difficult' → 'fr hg df'

The common word in both sentences is spanish, and the only common code word in both code sets is fr.
Therefore, 'spanish' is coded as 'fr'.