I suspect, but have yet to test it, that given the following distributional facts,
where, when, why replace the more formal structure of preposition + which in a relative clause:
Examples:
- That's the restaurant where we met for the first time.
(where = at/in which) - I remember the day when we first met.
(when = on which) - There was a very hot summer the year when he was born.
(when = in which) - Tell me (the reason) why you were late home.
(why = for which, but could replace the whole phrase 'the reason for which')
Source: edufind.com
by anaology,
1a. Factors influencing the way in which decisions are made.
1b. Factors influencing the way that decisions are made. <OK>
1c. Factors influencing how decisions are made.
2a. the degree to which
2b. the degree that <undecided; context would help>
3a. the extent to which
3b. the extent that <undecided; context would help>
Note that, the switch from preposition + which to 'that' might not work in all contexts. You'll have to test it. 

Originally Posted by
dihen What do you think of this one, ungrammatical or awkward?
"in English, which adjectives precede the noun" ('which' used as a relative pronoun)
I can't tell, dihen. I need more context. What's the complete sentence?