1 вариант

1.
-344 + ( -74 ) + 418 = -418 + 418 = 0
2.
-201 - 58 = -259
3.
x = -2 + ( -3 ) + 2 + 5
x = 2

противоположное x = -2

2 вариант
1.
-47 + 6 + ( -9 )  + 18 = -41 + ( -9) + 18 = -50 + 18 = -32
2.
-100 - ( -252 ) = 152
3.
x = 12 + ( -7 ) + 4 + 2
x = 11

противоположное x = -11