Question 318445
{{{x/(12-x)=5/15}}} Start with the given equation.



{{{15x=5(12-x)}}} Cross multiply.



{{{15x=60-5x}}} Distribute.



{{{15x+5x=60}}} Add {{{5x}}} to both sides.



{{{20x=60}}} Combine like terms on the left side.



{{{x=(60)/(20)}}} Divide both sides by {{{20}}} to isolate {{{x}}}.



{{{x=3}}} Reduce.



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Answer:


So the solution is {{{x=3}}} 



I leave the check for you.