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1.8100
2. 34 x 18 + 18 x 66
= 18 x ( 34 + 66)
= 18 x 100 = 1800
3. X × ( 8 + 12) = 160 + 20 × 12
= X x 20 = 160 + 240
= X x 20 = 400
X = 400 : 20 = 20
4. X x 12 - X x 2 = 2020
(12 - 2) x X = 2020
10 x X = 2020
X = 2020 : 10 = 202
a, X = 273
b, X = 156
c, X = 4
d, X = 505
e, X = \(\frac{37}{245}\)
\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)
= \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)
= \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)
= \(1-\frac{1}{7}\)
= \(\frac{7}{7}-\frac{1}{7}\)
= \(\frac{6}{7}\)
2) \(\frac{7}{4}-x.\frac{4}{3}=\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{7}{4}-\frac{5}{19}\)
\(x.\frac{4}{3}=\frac{133}{76}-\frac{20}{76}\)
\(x.\frac{4}{3}=\frac{113}{76}\)
\(x=\frac{113}{76}:\frac{4}{3}\)
\(x=\frac{399}{304}\)
VẬY \(x=\frac{399}{304}\)
b) \(\left(x+\frac{3}{4}\right).\frac{5}{7}=\frac{10}{9}\)
\(\left(x+\frac{3}{4}\right)=\frac{10}{9}:\frac{5}{7}\)
\(x+\frac{3}{4}=\frac{14}{9}\)
\(x=\frac{14}{9}-\frac{3}{4}\)
\(x=\frac{29}{36}\)
Vậy \(x=\frac{29}{36}\)
c) \(x.\frac{1}{2}+\frac{3}{2}.x=\frac{4}{5}\)
\(x.\left(\frac{1}{2}+\frac{3}{2}\right)=\frac{4}{5}\)
\(x.2=\frac{4}{5}\)
\(x=\frac{4}{5}:2\)
\(x=\frac{2}{5}\)
Vậy \(x=\frac{2}{5}\)
Chúc bạn học tốt !!!
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c) (2008 - 8) : 2 + 1 = 1001
1/2 + 1/6 + 1/12 + 1/20 + 1/30 1/x = 41/42
5/6 + 1/x = 41/42
1/x = 41/42 - 5/6
1/x = 1/7
vậy x = 7
`( 42 - x ) : 9 + 1 = 4`
`( 42 - x ) : 9 =4-1`
`( 42 - x ) : 9 =3`
`42-x=3xx9`
`42-x=27`
`x=42-27`
`x=15`
Vậy `=15`
`55 - 5 xx ( x + 1 ) = 20`
`5 xx ( x + 1 ) =55-20`
`5 xx ( x + 1 ) =35`
`x+1=35:5`
`x+1=7`
`x=7-1`
`x=6`
Vậy `x=6`
`164 - 64 : ( 12 + x ) = 160`
` 64 : ( 12 + x ) =164-160`
` 64 : ( 12 + x ) =4`
`12+x=64:4`
`12+x=16`
`x=16-12`
`x=2`
Vậy `x=2`
`@` `\text {Ans}`
`\downarrow`
`(42 - x) \div 9 + 1 = 4`
` (42 - x) \div 9 = 4 - 1`
` (42 - x) \div 9 = 3`
` 42 - x = 3 \times 9`
` 42 - x = 27`
` x = 42 - 27`
` x = 15`
______
`55 - 5 \times ( x + 1 ) = 20`
`5 \times (x+1) = 55 - 20`
`5 \times (x+1) = 35`
`x + 1 = 35 \div 5`
`x + 1 = 7`
`x = 7 - 1`
`x = 6`
______
`164 - 64 \div ( 12 + x ) = 160`
`64 \div (12 + x) = 164 - 160`
`64 \div (12 + x) = 4`
`12 + x = 64 \div 4`
`12 + x = 16`
`x = 16 - 12`
`x = 4`
`@` `\text {Kaizuu lv uuu}`