## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$8$
The generalized basic counting principle says that an event $e_1$ can be performed in $n_1$ ways and an event $e_2$ can be performed in $n_2$ ways, then there are $n_1n_2$ ways of performing them together. This can easily be extended to $n$ events. Here we have $2$ choices for all $3$ digits, thus using the generalized basic counting principle the number ways: $2^3=8$