a) \(30+\left(-30\right)+7\)

\(=30-30+7\)

\(=0+7\)

\(=7\)

b) \(12+\left(-31\right)\)

\(=12-31\)

\(=-31+12\)

\(=-\left(31-12\right)\)

\(=-19\)

c) \(\left(-40\right)+\left(-20\right)+\left(-40\right)\)

\(=-40-20-40\)

\(=-\left(40+20\right)-40\)

\(=-60-40\)

\(=-\left(60+40\right)\)

\(=-100\)

d) \(13+\left|-13\right|\)

\(=13+13\)

\(=26\)

e) \(\left|-13\right|+\left|-12\right|+\left|-17\right|\)

\(=13+12+17\)

\(=25+17\)

\(=42\)

f) \(-17+\left|-17\right|+12\)

\(=-17+17+12\)

\(=-\left(17-17\right)+12\)

\(=-0+12\)

\(=-\left(0-12\right)\)

\(=-\left(-12\right)\)

\(=12\)

a=-40

b=12

c=0

d=8

e=2960

Bài 1:

a, 30 + ( -30 ) + 7

b, 12 + ( -31 )

c, ( -40 ) + ( -20 ) + ( -40 )

d, 13 + | -13 |

e, | -13 | + | -12 | + | -17 |

f, -17 + | -17 | + 12

Nhanh lên nhé ! Mai mình nộp rồi. Cảm ơn