1) 6+8х=-х+33
8х+х=33-6
9х=27
х=27/9
х=3
2) -12х-18+9х=-9
-12х+9х=-9+18
-3х=9
х=9/(-3)
х=-3
Ответ:
870-(36-9)+23=866
870-27+23=866