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12(x - 6) = 4x + 12
12x - 72 = 4x + 12
12x - 4x = 12 + 72
8x = 84
x = 84 : 8
x = 21/2
Đề: Tìm x
\(12\times\left(x-6\right)=4\times x+12\)
\(12\times x-12\times6=4\times x+12\)
\(12\times x-72=4\times x+12\)
\(12\times x-4\times x=72+12\)
\(8\times x=84\)
\(x=84:8\)
\(x=10,5\)
\(12\times\left(x-6\right)=4\times x+12\)
\(12\times x-72=4\times x+12\)
\(12\times x-4\times x=12+72\)
\(8\times x=84\)
\(x=10,5\)
(3/7 + x) : 4/9 = 12/13
3/7 + x = 12/13 . 4/9
3/7 + x = 16/39
x = 16/39 - 3/7
x = -5/273
\(\left(\frac{3}{7}+x\right):\frac{4}{9}=\frac{12}{13}\)
\(\frac{3}{7}+x=\frac{12}{13}\cdot\frac{4}{9}\)
\(\frac{3}{7}+x=\frac{160}{117}\)
\(x=\frac{160}{117}-\frac{3}{7}\)
\(x=\frac{769}{819}\)
\(1-x=\frac{29}{12}+\frac{32}{8}\)
\(\Rightarrow1-x=\frac{77}{12}\)
\(\Rightarrow x=1-\frac{77}{12}=\frac{-65}{12}\)
\(\frac{31}{8}.x-\frac{11}{4}=\frac{42}{12}.\frac{10}{8}-\frac{1}{3}\)
\(\Rightarrow\frac{31}{8}.x-\frac{11}{4}=\frac{35}{8}-\frac{1}{3}\)
\(\Rightarrow\frac{31}{8}.x-\frac{11}{4}=\frac{97}{24}\)
\(\Rightarrow\frac{31}{8}.x=\frac{97}{24}+\frac{11}{4}=\frac{163}{24}\)
\(\Rightarrow x=\frac{163}{24}:\frac{31}{8}=\frac{163}{93}\)
`@` `\text {Ans}`
`\downarrow`
`a)`
`13/50 + 9% + 41/100 + 0,24`
`= 0,26 + 0,09 + 0,41 + 0,24`
`= (0,26 + 0,24) + (0,09 + 0,41)`
`= 0,5 + 0,5`
`= 1`
`b)`
`2018 \times 2020 - 1/2017 + 2018 \times 2019`
`= 2018 \times (2020 + 2019) - 1/2017`
`= 2018 \times 4039 - 1/2017`
`= 8150702`
`c)`
`1/2 + 1/6 + 1/12 + 1/20 +1/30 +1/42`
`=`\(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}\)
`=`\(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{6}-\dfrac{1}{7}\)
`=`\(1-\dfrac{1}{7}\)
`= 6/7`
\(a,\dfrac{13}{50}+9\%+\dfrac{41}{100}+0,24\\ 0,26+0,09+0,41+0,24\\ =\left(0,26+0,24\right)+\left(0,09+0,41\right)\\ =0,5+0,5\\ =1\\ b,2018\times2020-\dfrac{1}{2017}+2018\times2019\\ =2018\times\left(2020+2019\right)-\dfrac{1}{2017}\\ =2018\times4039-\dfrac{1}{2017}\\ =3150702-\dfrac{1}{2017}\\ c,\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}\\ =1-\dfrac{1}{2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\\ =1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}.........+\dfrac{1}{6}-\dfrac{1}{7}\\ =1-\dfrac{1}{7}\\ =\dfrac{6}{7}\)
( X - 39 ) x 4 : 9 = 12
( X - 39 ) x 4 = 12 x 9
( X - 39 ) x 4 = 108
X - 39 = 108 : 4
X - 39 = 27
X = 27 + 39
X = 66
\(\left(x-39\right).4:9=12\)
\(\left(x-39\right).4=12.9\)
\(\left(x-39\right).4=108\)
\(x-39=108:4\)
\(x-39=27\)
\(x=27+39\)
\(x=66\)