1) (40 910 + 1 090):(170-5 500:110)= 350
40910+1090=42000
5500:110=50
170-50=120
42000:120=350
2) (68 213-65 308)-4*308=1673
68213-65308=2905
4*308=1232
2905-1232=1673
3) (613 524:172+433)-625:5=3875
613524:172=3567
3567+433=4000
625:5=125
4000-125=3875