document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=66687>Question 66687</A>: <I><SPAN STYLE=\"word-break: break-all;\"> a two-digit number is twice the sum of its digit.  If the tens digit is 7 less than the unit digit, find the number. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #47324 by </B><A HREF=/tutors/aboutme.mpl?userid=ptaylor><B>ptaylor(2198)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ptaylor><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=ptaylor><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=47324\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> a two-digit number is twice the sum of its digit.  If the tens digit is 7 less than the unit digit, find the number.\r<BR>\n" );
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document.write( "Let x= the unit digit<BR>\n" );
document.write( "Then y= the tens digit<BR>\n" );
document.write( "And 10y+x= the number\r<BR>\n" );
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document.write( "x+y= the sum of the digits\r<BR>\n" );
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document.write( "Now we are told that 10y+x=2(x+y)  ------1st equation\r<BR>\n" );
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document.write( "We are also told that y=x-7  ----------- 2nd Equation\r<BR>\n" );
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document.write( "So our equations to solve are:\r<BR>\n" );
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document.write( "(1)  10y+x=2(x+y)<BR>\n" );
document.write( "(2)   y=x-7 \r<BR>\n" );
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document.write( "Substitute (2) into (1)\r<BR>\n" );
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document.write( "10(x-7)+x=2(x+x-7)  simplifying we have\r<BR>\n" );
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document.write( "10x-70+x=2x+2x-14  Collecting like terms:\r<BR>\n" );
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document.write( "11x-70=4x-14  subtract 4x from both sides and add 70 to both sides:\r<BR>\n" );
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document.write( "11x-4x=70-14<BR>\n" );
document.write( "7x=56<BR>\n" );
document.write( "x=8  the unit digit\r<BR>\n" );
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document.write( "Substite x=8 in (2):<BR>\n" );
document.write( "y=x-7=8-7;<BR>\n" );
document.write( "y=1 the tens digit\r<BR>\n" );
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document.write( "The 2 digit number is 10+8=18\r<BR>\n" );
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document.write( "ck\r<BR>\n" );
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document.write( "y=x-7<BR>\n" );
document.write( "1=8-7=1<BR>\n" );
document.write( "1=1<BR>\n" );
document.write( "18=2(8+1)<BR>\n" );
document.write( "18=18\r<BR>\n" );
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document.write( "Hope this helps ----ptaylor<BR>\n" );
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