Method 1:
[tex]p\%=\dfrac{p}{100}\\\\58\%=\dfrac{58}{100}=0.58\\\\n-a\ number\\\\0.58n=29\ \ \ \ |:0.58\\\\\boxed{n=50}[/tex]
Method 2:
[tex]\begin{array}{ccc}58\%&-&29\\100\%&-&n\end{array}\ \ \ \ \text{cross multiply}\\\\58n=2900\ \ \ \ |:58\\\\\boxed{n=50}[/tex]