Question

8,123-(2,123+1,8)
0,715+2,83+4,285+0,17

Answer 1

8,123-(2,123+1,8)=(8,123-2,123)+1,8=6+1,8=7,8
0,715+2,83+4,285+0,17=(0,715+4,825)+(2,83+0,17)=5,44+3=8,44

Answer 2

1) 8.123- 3.923= 4.2 
2) 3.545+ 4.285 + 0.17 = 7.83+ 0.17 = 8