a: =545x80-80x445

=8000

36 . 13 + 64 . 37 + 9 . 4 . 87 + 64 . 9 . 7

= 36 . 13 + 36 . 87 + 64 . 37 + 64 . 9 . 7

= 36( 13 +87 ) +  64 ( 37 + 63 )

= 36 . 100 + 64 . 100

= 3600 + 6400

= 10000

\(36.13+64.37+4.9.87+64.9.7=36.13+64.37+36.87+64.63=36\left(13+87\right)+64\left(37+63\right)=36.100+64.100=100\left(36+64\right)=100.100=10000\)

= 10 000

Lời giải:

$480:[75+(7^2-8.3):5]+2021=480:(75+25:5)+2021$

$=480:(75+5)+2021=480:80+2021=6+2021=2027$

\(480:\left[75+\left(7^2-8.3\right):5\right]+2021=480:\left[75+\left(49-24\right):5\right]+2021=480:\left[75+25:5\right]+2021=480:\left[75+5\right]+2021=480:80+2021=6+2021=2027\)

1.=545.(65+15-80)

=545.0

=0

2.=100:{250:[450-(4.125-4.25)]}

   =100:{250:[450-4.(125-25)]}

   =100:{250:[450-4.100]}

   =100:{250:50}

   =100:5

   =20

1. 545.65 + 545.15 - 80.445

= 545(65+15)-80.445

= 545.80-80.445

= 80.(545-445)

= 80.100

= 8000

a)=-7/21+8/24

=-1/3+1/3

=0

b)=-3/5.(2/7+5/7)+23/5

=-3/5.7/7+23/5

=-3/5.1+23/5

=-3/5+23/5

=20/5=4

c)=75/100-11/2+5/10:5/12+1/4

=3/4-11/2+1/2:5/12+1/4

=3/4+-11/2+1/2.12/5+1/4

=3/4+-22/4+6/5+1/4

=-19/4+6/5+1/4

=(-19/4+1/4)+6/5

=-18/4+6/5

=-9/2+6/5

=-45/10+12/10

=-23/10

\(a,\dfrac{-13}{5}-\dfrac{-7}{15}.\dfrac{120}{63}+\dfrac{4}{5}\\ =\dfrac{-13}{5}+\dfrac{8}{9}+\dfrac{4}{5}\\ =\dfrac{-77}{45}+\dfrac{4}{5}\\ =\dfrac{-41}{45}\\ b.\left(7\dfrac{5}{9}+2\dfrac{2}{3}\right)-5\dfrac{2}{9}\\ =\left(\dfrac{68}{9}+\dfrac{8}{3}\right)-\dfrac{47}{9}\\ =\dfrac{92}{9}-\dfrac{47}{9}\\ =5\)

2)\(-\dfrac{13}{5}--\dfrac{7}{15}.\dfrac{120}{63}+\dfrac{4}{5}\)
\(=-\dfrac{13}{5}+\dfrac{7.15.8}{15.9.7}+\dfrac{4}{5}\)
\(=-\dfrac{13}{5}+\dfrac{8}{9}+\dfrac{4}{5}\)
\(=\left(-\dfrac{13}{5}+\dfrac{4}{5}\right)+\dfrac{8}{9}\)
\(=-\dfrac{9}{5}+\dfrac{8}{9}\)
\(=\dfrac{-81+40}{45}=-\dfrac{41}{45}\)
3)\(\left(7\dfrac{5}{9}+2\dfrac{2}{3}\right)-5\dfrac{2}{9}\)
\(=\left(7\dfrac{5}{9}-5\dfrac{2}{9}\right)+2\dfrac{2}{3}\)
\(=2\dfrac{1}{3}+2\dfrac{2}{3}\)
\(=5\)

a,−135−−715.12063+45=−135+89+45=−7745+45=−4145b.(759+223)−529=(689+83)−479=929−479=5a,−135−−715.12063+45=−135+89+45=−7745+45=−4145b.(759+223)−529=(689+83)−479=929−479=5

Bài 2:

a: \(\Leftrightarrow x:\dfrac{4}{5}=\dfrac{-4}{6}+\dfrac{3}{6}=\dfrac{-1}{6}\)

=>x=-1/6*4/5=-4/30=-2/15

b: =>1/6x=5/6-7/12+1/3=10/12-7/12+4/12=7/12

=>x=7/2

c: =(47/11-3x)*11/5=-21/5

=>47/11-3x=-21/5:11/5=-21/11

=>3x=68/11

=>x=68/33