10. Write the number $a_{0}=9.3 \pm 0.5$ using a double inequality.
Solution. $9.3-0.5 \leqslant a_{0} \leqslant 9.3+0.5 ; 8.8 \leqslant a_{0} \leqslant 9.8$.

11-18. Write the numbers in the form of a double inequality: