1.(2998+839)*50-49=3837*50-49=191850-49=191801
2.2998+839*50-49=2998+41950-49=44948-49=44899
3.2998+839*(50-49)=2998+839*1=2998+839=3837
4.(1092-648):4*2=444:4*2=111*2=222
5.1092-648:(4*2)=1092-648:8=1092-81=1011
6.1092-648:4*2=1092-162*2=1092-324=768