Can you please write the isomer name though? I will draw it from that.
Write an isomer of structure for a), b) and c) and name them.
a) 3,3-dimethylpentane
b)3-methyl-4-ethyl-1-hexyne
c)3,3,4-trimethyl-1-pentene
CH3-CH2-C(CH3)2-CH3-CH3 is the 3-3 dimethylpentane. So just move one of the methyl groups to make it
2,3-dimethylpentane or
2,4-dimethylpentane or put both CH3 group on the 2 C to make
2,2-dimethylpetane.
For 3-methyl-4-ethyl-1-hexyne why not put methyl group on 3 and ethyl on 4?
Or CH3 on 3 and ethyl on 5. I think you must be making this harder than it is. If you will tell me what's giving you trouble perhaps I can clear it up.