a) 2 x 39 x 5

= 39 x (2 x 5)

= 39 x 10 = 390

b) 302 x 16 + 302 x 4

= 302 x ( 16 +4)

= 302 x 20 = 6040

c) 769 x 85 – 769 x 75

= 769 x (85 – 75)

= 769 x 10 = 7690

302 x 16 + 302 x 4

= 302 x ( 16 +4)

= 302 x 20 = 6040

\(4998\div7^2=302-2×\left(58×x-16\right)\)

\(102=302-2×\left(58×x-16\right)\)

\(2×\left(58×x-16\right)=302-102\)

\(2×\left(58×x-16\right)=200\)

\(58×x-16=200\div2=100\)

\(58×x=100+16=116\)

\(x=116\div58\)

\(x=2\)

Vậy...

Lê Quang Phúc 

bài 1:Tính nhanh

b)58+42+32nhân 8+5 nhân 16

c)(42 nhân 43+46nhân 57+43)-360:4

bài 2:tìm x

a)890:x=35 dư 15

c)1482:x+23=80

1: \(5\cdot25\cdot2\cdot16\cdot4=10\cdot25\cdot4\cdot16=10\cdot100\cdot16=16000\)

2: \(25\cdot5\cdot4\cdot2\cdot27\)

\(=25\cdot4\cdot5\cdot2\cdot27\)

\(=100\cdot10\cdot27=27000\)

3: \(2^3\cdot17-2^3\cdot17=2^3\left(17-17\right)=0\)

4: \(58\cdot75+58\cdot50-58\cdot25\)

\(=58\left(75+50-25\right)\)

\(=58\cdot100=5800\)

7: \(5\cdot23+35\cdot41+64\cdot65\)

\(=5\left(23+7\cdot41\right)+64\cdot65\)

\(=5\cdot310+64\cdot65=1550+4160=5710\)

a) 2 x 39 x 5

= ( 2 x 5 ) x 39

= 10 x 39

= 390

b) 302 x 16 + 302 x 4

= 302 x ( 16 + 4 )

= 302 x 20

= 302 x 2 x 10

= 604 x 10

= 6040

a. X=-124

b.x=-2

c. X= 298

D. X=-15

a) -124

b) -2

c) 298

d) -15

Chúc bạn học tốt!