## Precalculus (10th Edition)

$0.4$
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 $n(E)=5+35=40$ houses with an income less than $20000\$$, in total we have$n(S)=100$houses, therefore$\text{probability}=\frac{40}{100}=0.4.\$