The sufficiency & application of Scripture
24a) Scripture is the believer’s sufficient guide for all of faith and practice
Scripture is called profitable in the Bible, but it is not called sufficient. It is through “knowledge of Him” that we get “all things pertain to life and Godliness” – not through Scripture. And the Spirit guides us in all truth (John 16:13), and should thus be called our guide. To call God sufficient is biblical, to call the Bible – without mentioning God’s help – sufficient, is not. The Bible is not God.
b) and Christians must believe and obey whatever it teaches and commands.
That is a biblical view, whether the words "Christians must obey the Bible" appear in the Bible or not. A high view of the Bible is the hinge on which a biblical world view hangs.
c) The Bible provides the Christian … all that is necessary to make wise decisions concerning the many ethically complex issues of life.
Not all. See 24a).
Here is a simple example: It would be ethical and wise for a judge to listen to both sides, and judge justly. (Prov. 24:23, among others) The Bible don't give the judge party A's words or party B's words, but their testimonies help a Christian judge to make a wise decision.
In that way, all kinds of knowledge, from outside and inside the Bible, help us make wise decisions concerning ethics. We should consider everything we know in light of biblical guidelines, in the power of the Spirit. The Spirit and the facts are necessary too, not just the Bible.
Through precept and principle, the Bible provides a lot of what God will use to help the Christian make wise decisions. But not all. It gives the letter, but not the Spirit At times, God leads in other ways.
Other ways Christians understand this:
Some Christians say that precisely because Christians should have a high regard of scripture, they disregard the way the Tenets of Biblical Patriarchy proof-texts to get to the conclusions they want.