document.write( "Question 100104: three years ago mary was three times as old as her sister. now mary is twice as old as her sister. how old is mary now.
\n" ); document.write( "please show work \n" ); document.write( "
Algebra.Com's Answer #72874 by ptaylor(2198)\"\" \"About 
You can put this solution on YOUR website!
Let x=Mary's age now
\n" ); document.write( "And let y=her sister's age now
\n" ); document.write( "Then x-3=Mary's age three years ago\r
\n" ); document.write( "\n" ); document.write( "Now we are told that x-3=3(y-3)------------------eq1
\n" ); document.write( "and that:
\n" ); document.write( "x=2y-------------------------------------------------eq2\r
\n" ); document.write( "\n" ); document.write( "substitute x=2y into eq1 and we get:\r
\n" ); document.write( "\n" ); document.write( "2y-3=3(y-3) get rid of parens\r
\n" ); document.write( "\n" ); document.write( "2y-3=3y-9 add three and subtract 3y from both sides\r
\n" ); document.write( "\n" ); document.write( "2y-3y-3+3=3y-3y-9+3 collect like terms\r
\n" ); document.write( "\n" ); document.write( "-y=-6 divide both sides by -1\r
\n" ); document.write( "\n" ); document.write( "y=6--------------------Mary's sister's age now\r
\n" ); document.write( "\n" ); document.write( "substitute into eq2
\n" ); document.write( "x=2*6
\n" ); document.write( "x=12-----------------Mary's age now age now\r
\n" ); document.write( "\n" ); document.write( "CK\r
\n" ); document.write( "\n" ); document.write( "x-3=3(y-3)
\n" ); document.write( "12-3=3(6-3)
\n" ); document.write( "12-3=3*3
\n" ); document.write( "9=9
\n" ); document.write( "also
\n" ); document.write( "12=2*6
\n" ); document.write( "12=12\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Hope this helps---ptaylor
\n" ); document.write( " \n" ); document.write( "
\n" );