In a certain code language, 'you can go' is written as 'sat nat pat', 'they can join' is written as 'pat gat zat', and 'they are ready' is written as 'dat zat yat'. How will 'join' be written in that language?

Let's compare the sentences to isolate the code for 'join':
'you can go' → 'sat nat pat'

'they can join' → 'pat gat zat'
Comparing (1) and (2), the common word is 'can' and the common code is 'pat'. So, can=pat.

'they can join' → 'pat gat zat'

'they are ready' → 'dat zat yat'
Comparing (2) and (4), the common word is 'they' and the common code is 'zat'. So, they=zat.

In sentence (2), the remaining word is 'join' and the remaining code is 'gat'. Therefore, join=gat.