a: 86+357+14

=100+357

=457

b: \(3\cdot52-16:22\)

\(=156-\dfrac{8}{11}=\dfrac{1708}{11}\)

Bài 1:

a: \(A=15\cdot31\cdot2+5\cdot27\cdot6+10\cdot42\cdot3\)

\(=30\cdot31+30\cdot27+30\cdot42\)

\(=30\left(31+27+42\right)\)

\(=30\cdot100=3000\)

b: \(B=3\cdot5^2+160:\left(9-5\right)^2\)

\(=3\cdot25+160:4^2\)

=75+160:16

=75+10

=85

c: \(C=10^3\cdot\left\lbrace540-\left\lbrack6^3+\left(5\cdot4^2+104\right)\right\rbrack\right\rbrace\)

\(=1000\cdot\left\lbrace540-\left\lbrack216+5\cdot16+104\right\rbrack\right\rbrace\)

=1000{540-[216+80+104]

=1000*{540-400}

=1000*140

=140000

b: \(=15\left(141+19\right)=15\cdot160=24000\)

c: \(=2^3\cdot\left(17-14\right)=8\cdot3=24\)

464 + 38 + 536 + 162 + 250

= ( 464 + 536 ) + ( 38 + 162 ) + 250

= 1000 + 200 + 250

= 1450

d) Ta có: \(-8+\left(-14\right)+34+\left(-12\right)\)

\(=-8-14+34-12\)

\(=-20+20\)

\(=-0\)

e) Ta có: \(\left(-7\right)+\left(-20\right)+57+\left(-30\right)\)

\(=\left(-7+57\right)+\left(-20-30\right)\)

\(=50-50=0\)

f) Ta có: \(300-\left(-180\right)-120-42\)

\(=300+180-120-42\)

\(=258+60=318\)

d, Ta có : \(\left(-8\right)+\left(-14\right)+34+\left(-12\right)\)

\(=-\left(8+12\right)+34-14=-20+20=0\)

e, Ta có : \(\left(-7\right)+\left(-20\right)+57+\left(-30\right)\)

\(=-\left(30+20\right)+57-7=-50+50=0\)

f, Ta có : \(300-\left(-180\right)-120-42=318\)

(128-97+34)-(34-97+228)+2021^1

=(31+34)-[(-63)+228]+1

=65-165+1

=(-100)+1

=-99

mik gửi bạn lời giải , chúc bạn học tốt nhóe ! 

a)5.(-6).2.(-7)

=(5.2).[(-6).(-7)]

=10.42

=420

-17.25=-425

2.

5(-8).2(-3)=10.24=240

3(-5)²+2(-5)-20=15.5+(-2)5-4.5=(15-2-4).5=9.5=45

34.(15-10)-15(34-10)=34.15-34.10-15.34+15.10=0+(-34+15).10=-19.10=-190