(408:4*6-420:5)*100=408:(4*6)-(420:5)*100= ((408:24) - 84))*100 = (17-84)*100 = -6700
408:8*10-420:4*2=408:(8*10)-420:(4*2) = (408:80) - (420:8) = 5,1 - 52,5 = -47,4
1380:10:6-96:(48:4):2=(138:6)-(96:12) = 23 - 8 = 15
(1380-190*2):100+5990 =(1380-380):100+5990 = (1000 : 100) + 5990 = 10 + 5990 = 6000