Looking at Venn diagram when solving this question may help you to understand it better.

That is what we know when use statement (2) by itself:

Note that we know only that families in the state that have annual incomes over $50,000 and have a net worth over $500,000 (painted in dark) make 20% of the families in the state with an annual income over $50,000. But what percentage does it make out of total? We do not know, because we do not know what percentage out of total make families with an annual income over $50,000. Is 100%, or 50% or anything else?

But when we use statement (1) together with statement (2) we can answer the question: