[w451208]

How do you calculate multiplicity for a problem such as this?

[MissPhosgene]

You have to pay attention to what is said about the J values. They are different, but will be part of the same peak. I use something with the isobutyl functionality frequently and a 400 MHz NMR doesn't have the resolving power necessary to get a clear picture of the splitting.

Just think that you have a septet from the gem dimethyl group and a triplet from the methylene. 3 x 7 = 21.