In a certain code language, ‘what where how’ is written as ‘aa dd ff’; ‘where there that’ is written as ‘dd zz pp’ and ‘which what here’ is written as ‘ff kk ll’. How is ‘how’ written in that language?

To find the code for the word 'how', we can analyze the given statements and compare them to isolate the codes for each word.

Let us write down the given statements and their coded equivalents:
1. ‘what where how’ is written as ‘aa dd ff’
2. ‘where there that’ is written as ‘dd zz pp’
3. ‘which what here’ is written as ‘ff kk ll’

First, let us compare Statement 1 and Statement 2:
- Statement 1: ‘what where how’ → ‘aa dd ff’
- Statement 2: ‘where there that’ → ‘dd zz pp’
The common word in both statements is 'where', and the common code is 'dd'. Therefore, the code for 'where' is 'dd'.

Next, let us compare Statement 1 and Statement 3:
- Statement 1: ‘what where how’ → ‘aa dd ff’
- Statement 3: ‘which what here’ → ‘ff kk ll’
The common word in both statements is 'what', and the common code is 'ff'. Therefore, the code for 'what' is 'ff'.

Now, let us look at Statement 1 again:
- Word statement: ‘what’ + ‘where’ + ‘how’
- Code statement: ‘ff’ + ‘dd’ + ‘aa’ (in some order)
Since we have established that the code for 'where' is 'dd' and the code for 'what' is 'ff', the remaining word in Statement 1, which is 'how', must correspond to the remaining code, which is 'aa'.

Thus, the word ‘how’ is written as ‘aa’ in that language.