evaluate the number of carbon for the ffg. pairs by writing G if greater, L if less than or E if equal

1. butene E sym dimethylethylene
sol'n: butene has 4 carbons and sym dimethylethylene also has 4 carbons so it's equal. Am i right?
2. methylbutane L isopentane
methylbutane has 6 carbons? and isopentane 7? How can i compute the numbers of carbons? please help me

For all four of these, it is only the prefix for the longest chain and number of substituents that matters in determining the number of carbons.

In #1, butene has the prefix "but-", so therefore has four carbons in the longest chain.
Dimethylethylene also has four carbons, one from each methyl group ("di" - two, "methyl" - one carbon) and two from the ethylene backbone ("ethyl" - two carbons).

In #2, methylbutane has five carbons, one from the methyl group, and four from the butane chain.
Isopentane also has five carbons. The prefix "iso-" refers to a configuration of the molecule, and does not change the number of carbons present, just their arrangement. The second prefix "pent-" means five carbons.