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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x\times\left(4,5+1+0,5\right)=12,42\)
\(x\times6=12,42\)
\(x=2,07\)
vậy \(x=2,07\)
![](https://rs.olm.vn/images/avt/0.png?1311)
`y xx 3,2 + 6,8 xx y = 68,84 + 4,6`
`y xx ( 3,2 + 6,8 ) = 73,44`
`y xx 10 = 73,44`
`y = 73,44 : 10`
`y = 7,344`
y x (3,2 + 6,8) = 73,44
y x 10 = 73,44
y = 73,44 : 10
y = 7,344
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(x+x\right):2+\left(3,4+4,6\right)=5\cdot2\)
=>\(\dfrac{2x}{2}+8=10\)
=>x+8=10
=>x=2
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
12,42 x 3,5 + 2,07 x 6,5 + 3,15 x 20 + 6,85 x 20
= 2,07 x 6 x 3,5 + 2,07 x 6,5 + 3,15 x 20 + 6,85 x 20
= 2,07 x 21 + 2,07 x 6,5 + 3,15 x 20 + 6,85 x 20
= 2,07 x (21 + 6,5) + (3,15 + 6,85) x 20
= 2,07 x 27,5 + 10 x 20
= 56,925 + 200
= 256,925
12.42 x 3.5 + 2.07 x 6.5 x 3.15 x 20 + 6.85 x 20
=(2.07 x 6) x 3.5 + 2.07 x 6.5 x 20 x (3.15 + 6.85)
=2.07 x 6 x 3.5 + 2.07 x 6.5 x 20 x 10
=2.07 x (6 x 3.5 + 6.5 ) x 200
=2.07 x 27.5 x 200
=1138.5
![](https://rs.olm.vn/images/avt/0.png?1311)
\(4,6\times2+4,6\times9-4,6\)
\(=4,6\times2+4,6\times9-4,6\times1\)
\(=4,6\times\left(2+9-1\right)\)
\(=4,6\times10\)
\(=46\)
12,42 : ( 10 - x ) = 4,6
10 - x = 12,42 ; 4,6
10 - x = 2,7
x = 10 - 2,7
x = 7,3