Chapter 13 - Counting and Probability - 13.3 Probability - 13.3 Asses Your Understanding - Page 866: 64

$0.65$

We know that $\text{probability}=\frac{\text{number of favourable outcomes}}{\text{number of all outcomes}}=\frac{n(E)}{n(S)}.$ Hence here because we have $n(E)=35+30=65$ houses with an income between $10000\$$ and $29999\$$, in total we have $n(S)=100$ houses, therefore $\text{probability}=\frac{65}{100}=0.65.$