[Idiot1983]

The total carbons in 5 ethyl 4 methyl and 1 heptene. I got 21, is that right?
10+4+7=21

[BetaAmyloid]

Are the integers considering side carbon chains?

If not, and those are the number of ethyl, methyl, and heptene molecules to form the one large molecule, then the backbone of the molecule as a whole is 21.

[Tooter]

.

[BetaAmyloid]

Well usually, if the molecule is written as 5-ethyl-4-methyl-1-heptane then the 5, 4, and 1 represent where side chains are...which cause for the neccessity of what the r-groups are; but, if it is 5 ethyl 4 methyl 1 heptane, then it may be saying that the 5, 4, and 1 are needed to "become" an actual molecule and you would multiply the carbons. I am not sure what the question is asking or how it is written exactly.

If it was 5 ethyl...etc, then it would be 21 carbons. But, if it is 5-ethyl...etc, then we would need to know what the side chain (r-groups) are to find the carbon number.

[cth]

The total carbons in 5 ethyl 4 methyl and 1 heptene. I got 21, is that right?
10+4+7=21

Do you mean the compound 5-ethyl-4-methylhept-1-ene? Then, the numbers give the position along the chain of the substituants.

In your case, "hept" means 7 carbon atoms along the main chain. "ene" means a double bond placed onto the first C-C bond of the chain. "5-ethyl" means there is one ethyl group attached to the fifth carbon of the chain. "4-methyl" means there is a methyl attached to the fourth carbon.

With this name, you have the information needed to draw the molecule:

                  CH₃
                  |
H₂C=CH-CH₂-CH-CH-CH₂-CH₃
                        |
                        CH₂-CH₃