Answer
$68\%$
Work Step by Step
$\text{z-score}=\frac{\text{data item-mean}}{\text{standard deviation}}$
$|\frac{33-29}{4}|=|\frac{33-37}{4}|=1$, thus these are half the elements that are $1$ standard deviation away from the mean.
The normal distribution is symmetric about the mean. Thus using the 68-95-99.7 rule and the graph we get:
$P(\overline{x}-\sigma\leq x\leq\overline{x}+\sigma)=34\%+34\%=68\%$
