document.write( "Question 390719: Marcus has two sisters. The sum of the girls' ages is 13. The product of their ages is 36. How old is each sister? \n" ); document.write( "
Algebra.Com's Answer #277098 by checkley79(3341)\"\" \"About 
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X+Y=13
\n" ); document.write( "X=13-Y
\n" ); document.write( "XY=36
\n" ); document.write( "(13-Y)Y=36
\n" ); document.write( "13Y-Y^2=36
\n" ); document.write( "-Y^2+13Y-36=0
\n" ); document.write( "Y^2-13Y+36=0
\n" ); document.write( "(Y-9)(Y-4)=0
\n" ); document.write( "Y-9=0
\n" ); document.write( "Y=9 YEARS OLD ANS. FOR ONE SISTER
\n" ); document.write( "X+9=13
\n" ); document.write( "X=13-9
\n" ); document.write( "X=4 YEARS OLD ANS. FOR THE OTHER SISTER
\n" ); document.write( "Y-4=0
\n" ); document.write( "Y=4 ANS. DITTO.
\n" ); document.write( "X+4=13
\n" ); document.write( "X=13-4
\n" ); document.write( "X=9 DITTO.
\n" ); document.write( "PROOF:
\n" ); document.write( "4+9=13
\n" ); document.write( "13=13
\n" ); document.write( "4*9=36
\n" ); document.write( "36=36
\n" ); document.write( "
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