document.write( "Question 352560: if peter is 7 years older than sharon and john is twice as old as peter, work out how old peter is if the average of their ages is 19 \n" ); document.write( "

Algebra.Com's Answer #251940 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"p\"$ = Peter's age
\n" ); document.write( "Let $\"s\"$ = Sharon's age
\n" ); document.write( "Let $\"j\"$ = John's age
\n" ); document.write( "-----------------
\n" ); document.write( "given:
\n" ); document.write( "(1) $\"p+=+s+%2B+7\"$
\n" ); document.write( "(2) $\"j+=+2p\"$
\n" ); document.write( "(3) $\"%28p+%2B+s+%2B+j%29%2F3+=+19\"$
\n" ); document.write( "------------------
\n" ); document.write( "From (1):
\n" ); document.write( " $\"p+=+s+%2B+7\"$
\n" ); document.write( " $\"s+=+p+-+7\"$
\n" ); document.write( "Substitute (1) and (2) in (3)
\n" ); document.write( "(3) $\"%28p+%2B+s+%2B+j%29%2F3+=+19\"$
\n" ); document.write( " $\"%28p+%2B+p+-+7+%2B+2p%29%2F3+=+19\"$
\n" ); document.write( " $\"%284p+-+7%29%2F3+=+19\"$
\n" ); document.write( " $\"4p+-+7+=+57\"$
\n" ); document.write( " $\"4p+=+64\"$
\n" ); document.write( " $\"p+=+16\"$
\n" ); document.write( "Peter is 16
\n" ); document.write( "check answer:
\n" ); document.write( " $\"s+=+p+-+7\"$
\n" ); document.write( " $\"s+=+9\"$
\n" ); document.write( "and
\n" ); document.write( " $\"j+=+2p\"$
\n" ); document.write( " $\"j+=+32\"$
\n" ); document.write( "and
\n" ); document.write( "(3) $\"%28p+%2B+s+%2B+j%29%2F3+=+19\"$
\n" ); document.write( "(3) $\"%2816+%2B+9+%2B+32%29%2F3+=+19\"$
\n" ); document.write( " $\"57%2F3+=+19\"$
\n" ); document.write( " $\"57+=+57\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );