8.4% of 300 + 4. 8% of ? = 102

$frac{{8.4}}{{100}} imes 300 + frac{{4.8}}{{100}} imes ? = 102$

$frac{{4.8}}{{100}} imes ? = 102 - 25.2$

$? = frac{{76.8 imes 100}}{{4.8}} Rightarrow ? = 1600$