Answer: The required best estimate is 10.92.
Step-by-step explanation: We are given to best estimate the value of 21% of 52.
Let x represents the best estimate for the given percentage.
Then, according to the given information, we have
[tex]x\\\\=21\%\times52\\\\\\=\dfrac{21}{100}\times52\\\\\\=\dfrac{1092}{100}\\\\=10.92.[/tex]
Thus, the required best estimate is 10.92.