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162:x + 216:x = 6
(162 + 216):x = 6
378:x = 6
x = 378 : 6
x= 63
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a) 3885:(\(x\) x 21) =37.
(\(x\) x 21) = 3885 : 37
(\(x\) x 21) = 105
\(x\) = 105 : 21
\(x\) = 5.
Vậy \(x\) =5.
b) 162:x+216:x=6
(162 + 216) : x =6
378 : x = 6
x = 378 : 6
x = 63.
Vậy x = 63.
# HOK TỐT #
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a; (2 + 4+ 6 + 8 +...+ 98) x (210 x 12 + 420 - 420 x 7)
= (2 + 4 + 6 + 8 +..+ 98) x (210 x 2 x 6 + 420 - 420 x 7)
= (2 + 4 + 6 + 8 +...+ 98) x (420 x 6 + 420 - 420 x 7)
= (2 + 4 + 6 + 8+...+ 98) x [420 x (6 + 1 - 7)]
= (2 + 4 + 6 +...+ 98) x {420 x 0]
= (2 + 4 + 6 +...+ 98) x 0
= 0
b; 29 + 299 + 2999 + 29999 + 2999999
= 30 - 1 + 300 - 1 + 3000 - 1 + 30000 - 1+ 300000 - 1
= (30 + 300 + 3000 + 30000+ 300000) - (1 + 1 + 1 + 1 + 1)
= 333330 - 5
= 333325
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\(x\cdot1+x\cdot2+x\cdot3=900-420\)
\(x\cdot(1+2+3)=480\)
\(x\cdot6=480\rightarrow x=80\)
X x 1 + X x 2 + X x 3 = 900 - 420
X x ( 1 + 2 + 3 ) = 480
X x 6 = 480
X = 480 : 6
X = 80
![](https://rs.olm.vn/images/avt/0.png?1311)
TK :
978 : ( 7 × x - 18 ) - 216 = 2 + 4 + 6 + ..... + 20
978 : ( 7 × x - 18 ) - 216 = (20 + 2) x [ (20 - 2) : 2 + 1] : 2
978 : ( 7 × x - 18 ) - 216 = 22 x [ 18 : 2 + 1] : 2
978 : ( 7 × x - 18 ) - 216 = 22 x [ 9 + 1] : 2
978 : ( 7 × x - 18 ) - 216 = 22 x 10 :2
978 : ( 7 × x - 18 ) - 216 = 220 : 2
978 : ( 7 × x - 18 ) - 216 = 110
978 : ( 7 × x - 18 ) = 110 + 216
978 : ( 7 × x - 18 ) = 326
7 × x - 18 = 978 : 326
7 × x - 18 = 3
7 × x = 3 + 18
7 × x = 21
x = 21 : 7
x = 3
ta có : `2 + 4 + 6 + ..... + 20`
số số hạng là : `(20-2):2+1= 10`
tổng là : `(20+2) xx 10 :2=110`
`978 : ( 7 × x - 18 ) - 216 = 2 + 4 + 6 + ..... + 20`
`978 : ( 7 × x - 18 ) - 216 =110`
`978 : ( 7 × x - 18 )=110+216`
`978 : ( 7 × x - 18 )=326`
`7 × x - 18=978 :326`
`7 × x - 18=3`
`7 xx x=3+18`
`7 xx x=21`
`x=21:7`
`x=3`
vậy `x=3`
![](https://rs.olm.vn/images/avt/0.png?1311)
X x 62 - X x 52 = 420
X x ( 62 - 52 ) = 420
X x 10 = 420
X = 420 : 10
X = 42
X x 62 -X x52=420
X x (62-52)=420
X x10=420
=>x=42
k đúng ch0 mình nha mấy bạn
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a)
160 : (4 × 8) = 160 : 32 = 5
160 : 4 : 8 = 40 : 8 = 5
Vậy 160 : (4 × 8) = 160 : 4 : 8.
96 : (3 × 8) = 96 : 24 = 4
96 : 3 : 8 = 32 : 8 = 4
Vậy 96 : (3 × 8) = 96 : 3 : 8.
105 : (5 × 7) = 105 : 35 = 3
105 : 5 : 7 = 21 : 7 = 3
Vậy 105 : (5 × 7) = 105 : 5 : 7.
Nhận xét: a : (b × c) = a : b : c
b)
270 : (9 × 6) = 270 : 9 : 6 = 30 : 6 = 5
420 : (7 × 3) = 420 : 7 : 3 = 60 : 3 = 20
144 : (2 × 8) = 144 : 2 : 8 = 72 : 8 = 9
420 : x + 216 : x = 6
(420 + 216) : x = 6
636 : x = 6
x = 636 : 6
x = 106
Vậy x = 106
HT