Tìm x biết :
7,5×X+2,45×X=20
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Đáp án D
x + 73 : 5 = 20 + 7 , 5 × 4 x + 73 : 5 = 20 + 30 x + 73 : 5 = 50 x + 73 = 250 x = 250 - 73 x = 177
Vậy x=177
Đáp án cần chọn là: D
\(a,\frac{x+15}{x}=\frac{4}{3}\Rightarrow4x=3x+45\Leftrightarrow x=45\)
\(b,\frac{7,5-x}{3,5+x}=\frac{5}{6}\Rightarrow17,5+5x=45-6x\Leftrightarrow11x=27,5\Rightarrow x=2,5\)
\(c,\frac{x-20}{x-10}=\frac{x+40}{x+70}\Rightarrow\left(x-20\right)\left(x+70\right)=\left(x-10\right)\left(x+40\right)\)
\(\Leftrightarrow x^2+50x-1400=x^2+30x-400\)
\(\Leftrightarrow20x=1000\)
\(\Rightarrow x=50\)
a. \(\frac{\left(x+15\right)}{x}=\frac{4}{3}\Leftrightarrow4x=3\left(x+15\right)\Leftrightarrow4x=3x+45\Leftrightarrow x=45\)
Vậy x=45
b. \(\frac{7,5-x}{3,5+x}=\frac{5}{6}\Leftrightarrow5\left(3,5+x\right)=6\left(7,5-x\right)\Leftrightarrow17,5+5x=45-6x\Leftrightarrow11x=27,5\Leftrightarrow x=2,5\)
Vậy x=2,5
c. \(\frac{x+20}{x-10}=\frac{x+40}{x+70}\Leftrightarrow\left(x+40\right)\left(x-10\right)=\left(x+20\right)\left(x+70\right)\)
\(\Leftrightarrow x^2+30x-400=x^2+90x+1400\Leftrightarrow-60x=-30\Leftrightarrow x=-30\)
Vậy x=-30
a) x +/21 - 14/ = 35
x+7=35
x=35-7
x=28
Vậy x=28
b) 4,5 - x = 2,45
x=4,5-2,45
x=2,05
Vậy x=2,05
`1,`
`538 - x = 275`
`\Rightarrow x = 538 - 275`
`\Rightarrow x = 263`
Vậy, `x = 263`
`2,`
`45 - 9x = 18`
`\Rightarrow 9x = 45 - 18`
`\Rightarrow 9x = 27`
`\Rightarrow x = 27 \div 9`
`\Rightarrow x = 3`
Vậy, `x = 3`
`3,`
`(5x - 9) \div 3 = 12`
`\Rightarrow 5x - 9 = 12. 3`
`\Rightarrow 5x - 9 = 36`
`\Rightarrow 5x = 36 + 9`
`\Rightarrow 5x = 45`
`\Rightarrow x = 45 \div 5`
`\Rightarrow x = 9`
Vậy, `x = 9.`
1) \(538-x=275\)
\(x=538-275\)
\(x=263\)
2) \(45-9x=18\)
\(9x=27\)
\(x=3\)
3) \(\left(5x-9\right)\div3=12\)
\(\left(5x-9\right)=12\times3\)
\(5x-9=36\)
\(5x=45\)
\(x=9\)
`2,45xx46+8xx0,75xx54xx2,45xx0,5xx8`
`=2,45xx46+54xx2,45+8xx0,75+0,5xx8`
`=2,45xx(46+54)+8xx(0,75+0,5)`
`=2,45xx100+8xx1,25`
`=245+10`
`=255`
\(17,5\text{×}x-7,5\text{×}x=34,8\\ \left(17,5-7,5\right)\text{×}x=34,8\\ 10\text{×}x=34,8\\ x=34,8:10\\ x=3,48\)
Lời giải:
$7,5\times x+2,45\times x=20$
$x\times (7,5+2,45)=20$
$x\times 9,95=20$
$x=20:9,95=2,01$
7,5 x X + 2,45 x X = 20
X x (7,5 + 2,45) = 20
X x 9,95 = 20
X = 20 : 9,95 = 2,01