\(a.=24+42+120-24-42\)
\(=\left(24-24\right)+\left(42-42\right)+120\)
\(=0+0+120\)
\(=120\)
\(b.=13-145+49-13-49\)
\(=\left(13-13\right)+\left(49-49\right)-145\)
\(=0+0-145\)
\(=-145\)
a)(24+42)+(120-24-42)
= 24+42+120- 24-42
=(24-24)+(42-42)+120
=0+0+120
=120
b)(13-145+49)-(13+49)
= 13-145+49-13+49
= (13-13)+(49-49)+145
= 0+0+145
=145
c)25.22+(15-28)+(12-19+10)
=25.4+15-28+12-19+10
=100+(19-15)-(28+12)+10
=100+4-40+10
=94
# Hok_tôt