35+75+345-35-75
=(35-35)+(75-75)+345
=0+0+345
=345
23.75-130-20+25.23
=23.(75+25)-130-20
=23.100-130-20
=2300-130-20
=2150
1) (35 + 75) + (345 - 35 - 75)
= (35 - 35) + (75 - 75) + 345
= 0 + 0 + 345
= 345
2) 23 . 75 - 130 - ( 20 - 25 . 23)
= 23 . 75 - 130 - ( 20 - 575)
= 23 . 75 - 130 - (-555)
= 1725 - 130 - (-555)
= 1595 - (-555)
= 2150.
Chúc bạn học tốt!