[Solved] How to simplify these compound logical expression?

I’ll give you some hints, so as to not do your homework for you:

!(a || b || c) = (!a && !b && !c)

!(a && b && c) = (!a || !b || !c)

!(a == b) = (a != b)

!(a <= b) = (a > b)

You should be able to take it from there.