Question

1)8в+12в-21в+в 2)-13с+12с+40с-18с

Answer 1

1)8в+12в-21в+в=20в-20в=0
2)-13с+12с+40с-18с=
-с+22с=21с

Answer 2

1)8в+12в-21в+в=20в-21в+в=21в-21в=0
Или
1)8в+12в-21в+в=8в+12в+(-21в)+в=21в+(-21в)=0