Question

bỏ ngoặc rồi tính

a, (55 - 27 ) +(27+30 -55)

b, (75+35+15)-(15-75+35)

c, (2015 - 79+19) - (2020+80-91)

Answer 1

a) \(\left(55-27\right)+\left(27+30-55\right)\)

\(=55-27+27+30-55\)

\(=\left(55-55\right)+\left(-27+27\right)+30\)

\(=30\)

Answer 2

b) \(\left(75+35+15\right)-\left(15-75+35\right)\)

\(=75+35+15-15+75-35\)

\(=\left(75+75\right)+\left(35-35\right)+\left(15-15\right)\)

\(=75+75\)

\(=150\)

Answer 3

c) \(\left(2015-79+19\right)-\left(2020+80-91\right)\)

\(=2015-79+19-2020-80+91\)

\(=\left(2015-79\right)+\left(19+91\right)-\left(2020+80\right)\)

\(=1936+110-2100\)

\(=-54\)