220/(1+10/100).(1-20/100)

$$ \frac{220}{\left(1+\frac{10}{100}\right)\cdot\left(1-\frac{20}{100}\right)}=\frac{220}{\left(\frac{100+10}{100}\right)\cdot\left(\frac{100-20}{100}\right)}=\frac{220}{\frac{110}{100}\cdot\frac{80}{100}}=\frac{220}{\frac{22}{25}}=\frac{220}{1}\cdot\frac{25}{22}=10\cdot25=250 $$ 250 is the right answer.