?% of (584.2−244.2)=(9 ) 2 +21

$frac{?}{{100}} imes left( {584.2 - 244.2} ight)$ = 81+21

$Rightarrow frac{?}{{100}} imes 340 = 102$

$Rightarrow ? = frac{{102 imes 100}}{{340}} = 30$