Question 1135500
{{{(0.4*10+0.1x)/(x+10)=0.3}}}

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{{{4+0.1x=0.3x+3}}}

{{{4-3=0.2x}}}

{{{x=1/0.2}}}

{{{highlight(x=5)}}}


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check
{{{0.4*10+0.1*5=0.3*15}}}
{{{4+0.5=0.1*45}}}
{{{4.5=4.5}}}