\(a,31.\left(-18\right)+31.\left(-81\right)-31\)

\(=31\left(-18-81-1\right)\)

\(=31\left(-100\right)\)

\(=-3100\)

\(b,13\left(23+22\right)-3\left(17+28\right)\)

\(=299+286-51-84\)

\(=450\)

Cảm ơn

A) 

y:5=(118+338)

y:5=456

y=456x5

y=2280

b)

yx6=972-108x4

yx6=972-432

yx6=540

y=540:6

y=90

C)
y+8:4=28+204

y+2=232

y=232-2

y=230

tk nha!

A,285                        B,540                     C,920

\(\dfrac{18}{17};\dfrac{298}{289};\dfrac{2002}{1999}\)

Phân số lớn hơn 1 là:\(\dfrac{18}{17};\dfrac{298}{289};\dfrac{2002}{1999}\)

298/289; 18/17 ; 2001/1999

2001/1999

a, Ta có: 10 = 2.5; 12 =  2 2 .3

BCNN(10,12) = 2 2 .3.5 = 60

b, Ta có: 24 =  2 3 .3; 56 =  2 3 .7

BCNN(24;56) =  2 3 .3.7 = 168

c, Ta có: 84 =  2 2 .3.7; 108 =  2 2 . 3 3

BCNN(84;108) =  2 2 . 3 3 .7

d, Ta có: 33 = 3.11; 44 = 4.11; 55 = 5.11

BCNN(33;44;55) = 3.4.5.11 = 660

e, Ta có: 8 =  2 3 ; 18 = 2. 3 2 ; 30 = 2.3.5

BCNN(8,18,30) =  2 3 . 3 2 . 5 = 360

f, Ta có: 40 =  2 3 . 5 ; 28 =  2 2 .7; 140 =  2 2 .5.7

BCNN(40;28;140) =  2 3 . 5 . 7 = 280

gfvbh