7+(-8)-(-12)-(-7)+12-30; 2 целых 3/4-(-1 цнлая 1/2)+(-5/6)

7+(-8)-(-12)-(-7)+12-30 = 7-8+12+7+12-30= 0;

2 целых 3/4-(-1 цнлая 1/2)+(-5/6) = 2 9/12 + 1 6/12 - 10/12 = 3 5/12