205. It is required to find a number which, when multiplied by itself, added to two, then doubled, added to three again, divided by 5, and finally multiplied by 10, results in 50.
205. $\frac{50}{10}=5 ; 5 \cdot 5=25 ; 25-3=22 ; 11-2=9 ; \sqrt{9}=3$.