Answer
$64$
Work Step by Step
In the previous answer(Q -24), we found that $T_n = 2^{n-1}$ where $T_n$ is the number of bit strings of length n with an even number of 0s.
So, number of bit strings of length 7 with an even number of 0s = $2^{7-1} = 2^6 = 64$.
Thus, there are 64 bit-strings of length 7 with an even number of 0s
