Question 1088081
x, time for pipe
x+10, time for the first pipe


{{{1/x+1/(x+10)=1/12}}}

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{{{12x(x+10)(1/x+1/(x+10))=12x(x+10)(1/12)}}}

{{{12(x+10)+12x=x(x+10)}}}

{{{12x+120+12x=x^2+10x}}}

{{{24x+120=x^2+10x}}}


{{{x^2-14x-120=0}}}

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discriminant,  {{{196+4*120=196+480=676=26^2}}};

{{{x=(14+- 26)/2}}}, but only the PLUS form will work.

{{{x=20}}}


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first pipe alone,  20 minutes
second pipe alone,  30 minutes
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