What is the correct way to name alkanes with multiple branches?

[Suzyscans]

1. This is my first posting, I am having trouble naming alkanes. I believe my first two problems are correct, but am unsure. The third problem I am having trouble with. I am just not sure what to name the branches coming off the carbon chain.
2.

1. (CH3)2CHCH(CH3)2 2. CH2Ch2CH2CH3
l
CH3CH2CH2CHCH2C--H
l l
CH3CH2 H3.
CH3 H
l l
CH3CH2CH2CH2--C--C--CH2CH3
l l
CH2 CH3
l
CH3

3. Problem 1 :4-carbon chain makes it butane. The branches at both C2 and C3 are methyl, so the name is 2,3-dimethylbutane.

Problem 2: 6-carbon chain makes it hexane. The branch at C2 is butyl. The branch at C3 is ethyl, so the name is 2-butyl-3-ethylbutane.

Problem 3:
8-carbon chain= octane
branch at C3 is methyl
branches at 4C are methyl and ethyl
That is where I get stuck on the name. Is it 4-ethyl-4,3-dimethyloctane??

Thanks very much for your input!

 

[Suzyscans]

I can't get the equations to display properly! I will edit as soon as I figure it out :)

 

[chemisttree]

You have 1) correct.