(36.8-15.3)*0.4+0.6*12.4-(18.6-13.8)*0.5=13.64; 1)36.8-15.3=21.5; 2)18.6-13.8=4.8; 3)21.5*0.4=8.6; 4)4.8*0.5=2.4; 5)0.6*12.4=7.44; 6)8.6+7.44=16.04; 7)16.04-2.4=13.64;