document.write( "Question 273605: a two-digit number is twice the sum of its digits. if the tens digit is 7 less than the unit digit. find the number \n" ); document.write( "

Algebra.Com's Answer #199827 by josmiceli(19441) $\"\"$ $\"About$

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Call the units digit $\"u\"$
\n" ); document.write( "and the tens digit $\"t\"$
\n" ); document.write( "given:
\n" ); document.write( " $\"10t+%2B+u+=+2%2A%28t+%2B+u%29\"$
\n" ); document.write( " $\"t+=+u+-+7\"$
\n" ); document.write( "---------------
\n" ); document.write( "Substitute
\n" ); document.write( " $\"10%2A%28u+-+7%29+%2B+u+=+2%2A%28u+-+7+%2B+u%29\"$
\n" ); document.write( " $\"10u+-+70+%2B+u+=+2u+-+14+%2B+2u\"$
\n" ); document.write( " $\"11u+-+4u+=+70+-+14\"$
\n" ); document.write( " $\"7u+=+56\"$
\n" ); document.write( " $\"u+=+8\"$
\n" ); document.write( " $\"t+=+u+-+7\"$
\n" ); document.write( " $\"t+=+8+-+7\"$
\n" ); document.write( " $\"t+=+1\"$
\n" ); document.write( "The number is 18
\n" ); document.write( "check:
\n" ); document.write( " $\"10t+%2B+u+=+2%2A%28t+%2B+u%29\"$
\n" ); document.write( " $\"10%2A1+%2B+8+=+2%2A%281+%2B+8%29\"$
\n" ); document.write( " $\"10+%2B+8+=+2%2A9\"$
\n" ); document.write( " $\"18+=+18\"$
\n" ); document.write( "OK \n" ); document.write( "

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