1. 16×12+34×17-28×20=210
16×12=192
34×17 =578
28×20 =560
192+578=770
770-560=210
2. 909:9-(520-502)×13:6=62
520-502 =18
909:9=101
18×13=234
234:6=39
101-39=62
3. 755:5+18×18-(89-73)×19=171
89-73=16
16×19=304
755:5=151
18×18=324
151+324=475
475-304=171
4. (22×44-11×20-10×10):8=81
22×44=968
11×20=220
10×10=100
968-220-100=648
648:8=81