Answer
$0.5$
Work Step by Step
$\text{z-score}=\frac{\text{data item-mean}}{\text{standard deviation}}$
Hence here the z-score is: $\frac{64-64}{7}\approx 0$
Then, using the table: $P(x\leq 64)\approx P(z\leq 0)=0.5$
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