Answer
$69.15\%$
Work Step by Step
$\text{z-score}=\frac{\text{data item-mean}}{\text{standard deviation}}$
Hence here the z-score is: $\frac{13-12}{2}=0.5$
Then, using the table: $P(x\leq13)\approx P(z\leq0.5)=0.6915=69.15\%$
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