Statutory Codes
The laws of intestacy are included within the probate code of each state. This site includes questions that apply the Uniform Probate Code and California Probate Code.
Uniform Probate Code (UPC)
The UPC is model legislation drafted by the Uniform Law Commission. A copy of the text is available to download from the ULC website (Search Acts for Uniform Probate Code). The intestacy provisions are in Article II, Part I.
California Probate Code (CPC)
You can find a free online version of the CPC here. Division 6, Part II governs intestate succession. Note that to apply the laws of intestacy for a married decedent, you also need to be able to distinguish between community property, quasi-community property, and separate property. Division 4, Part II of the Family Code provides definitions of those terms. When you face practice problems involving intestate married decedents, keep in mind that a surviving spouse owns some property via the operation of community property and inherits other property via intestacy.
Other Relevant Provisions
In these practice problems, all kin relationships are legally clear. That is, if the problem indicates that someone is a 'child' of the decedent, you may assume that the parent-child relationship has been legally established and is not in question. In practice, that may not be true and you may need to investigate the issue further.
In addition, all property included within a decedent's estate in these problems is assumed to be probate property and subject to the laws of intestacy. Again, real life (or even law school exams) may involve additional complexity. Keep in mind that certain property ownership arrangements or other legal instruments may prevent the application of the laws of intestacy.