document.write( "Question 825667: manu is 4 years older than his sister anu. if the sum of their ages is 20 years, find their ages. \n" ); document.write( "
Algebra.Com's Answer #497539 by homeworkhedgehog(9)\"\" \"About 
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For this, you can create two equations and solve them using substitution or elimination.\r
\n" ); document.write( "\n" ); document.write( "\"Manu is 4 years older than his sister Anu\" translates to
\n" ); document.write( "M = 4 + A\r
\n" ); document.write( "\n" ); document.write( "\"The sum of their ages is 20 years\" translates to
\n" ); document.write( "M + A = 20 \r
\n" ); document.write( "\n" ); document.write( "Since we know that M = 4 + A, we can substitute that into \"M\" in the other equation:
\n" ); document.write( "(4 + A) + A = 20\r
\n" ); document.write( "\n" ); document.write( "Now we combine our \"like\" terms (the parentheses are negligible):
\n" ); document.write( "4 + 2A = 20\r
\n" ); document.write( "\n" ); document.write( "And solve for \"A\" using algebra.
\n" ); document.write( "Subtract 4 from both sides:
\n" ); document.write( "2A = 16\r
\n" ); document.write( "\n" ); document.write( "Divide both sides by 2:
\n" ); document.write( "A = 8\r
\n" ); document.write( "\n" ); document.write( "Now we know how old Anu is. She is 8 years old. We use this to find Manu's age. \"Manu is 4 years older than Anu\" tells us that Manu is 12. This checks out when we add 8 and 12 to see if their combined age is really 20 like the problem says.
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