Need some clarifications with nor

[doctortt]

From the old days, I was taught to use nor this way:
"They don't know how to do x nor do they know how to do y."

In Kaplan, the correct answer of the question says "They don't know how to X or how to Y."

One of the incorrect answer choices is "They don't know how to X nor how to Y."

I'm wondering why the nor answer choice is incorrect. Obviously, the structure is different than what I learned in the old days.

[rs2010]

Stick to GMAT rules and this is defined in GMAT rules.

Idiom is x or y not x nor y. you can use nor with neither. One more thing
the structure is different than what I learned in the old days is incorrect it should be the structure is different from what I learned in the old days.

[doctortt]

Yes you're right. It's different from. That's why I'm studying now.