84(4\19)*1.375+105(5\19)*0.9

84又4/19×1.375＋105又5/19×0.9
=（85-5/19）*1.375+（105+5/19）*0.9
=85*1.375-5/19*1.375+105*0.9+5/19*0.9
=85*11/8+94.5-5/19*0.475
=210.25

84*(4/19)*1.375+105(519)*0.9
=84*(4/19)*(11/8)+105*(5/19)*(9/10)
=42*11*2/38+105*9/38
=自己算
简算?把19当20算...那就很简单啦