Tìm x, biết: 40% * x + x * 20% = 72
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a) \(40\%\times x+x\times20\%=72\)
\(\left(40\%+20\%\right)\times x=72\)
\(60\%\times x=72\)
\(0,6\times x=72\)
\(x=72:0,6\)
\(x=120\)
b) \(x-20\%\times x=216\)
\(x\times\left(1-20\%\right)=216\)
\(x\times80\%=216\)
\(x\times0,8=216\)
\(x=216:0,8\)
\(x=270\)
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72+40/9 = x+x*1/7
688/9 =x*(1+1/7)= x*8/7
x = 688/9 : 8/7 = 602/9
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\(X\times20o/o+X=7,2\)
\(\Leftrightarrow\)2x+0,2=7,2
\(\Leftrightarrow\)2x =7,2-0,2
\(\Leftrightarrow\)2x = 7
\(\Rightarrow\) x =7:2
\(\Rightarrow\)x =3,5
\(40o/o\times X+X\times20o/o=72\)
\(\Leftrightarrow0,4\times X+X\times0,2=72\)
\(\Leftrightarrow X\times\left(0,4+0,2\right)=72\)
\(\Leftrightarrow X\times0,6=72\)
\(\Rightarrow X=72:0,6\)
\(\Rightarrow X=120\)
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x + 20% * x = 7.2
x +1/5 * x = 7.2
x * ( 1 + 1/5 ) = 7.2
x * 1.2 = 7.2
x = 7.2 : 1.2
x = 6
40% * x + x * 20% = 72
2/5 * x + x * 1/5 = 72
( 2/5 + 1/5 ) * x = 72
0.6 * x = 72
x = 72 : 0.6
x = 120
![](https://rs.olm.vn/images/avt/0.png?1311)
40% = 0,4
20% = 0,2
0,4 * x + x * 0,2 = 72
( 0,4 + 0,2 ) * x = 72
0,6 * x = 72
x = 72 : 0,6
x = 120