document.write( "Question 333422: For the problem I have to solve it says I have to write a system of equations involving two equations in two variables then to solve the system. Here is the problem: Jean is twice as old as Michael. The sum of their ages 3 years ago was 45 years. Find their ages now.
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document.write( "I tried to solve it without the sytem of equations and i got the answer of jean:32 and Michael:16 but then I realized I would get the question wrong if I didn't show the system of equations. Please help me. \n" );
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Algebra.Com's Answer #238919 by jrfrunner(365)![]() ![]() You can put this solution on YOUR website! first, your answers, of Jean=32 and Michael 16, have you tested them to see if they are correct? The sum of their ages 3 years ago was 45 years \n" ); document.write( "Let see, 3 years ago Jean=32-3=29, Michael=16-3=13 so their sum is 42, so your answers are incorrect! \n" ); document.write( "--- \n" ); document.write( "Begin by letting J=Jean's age and M=Michaels age, you have two unknowns J and M \n" ); document.write( "and you need as many equations as unknowns. \n" ); document.write( "-- \n" ); document.write( "Jean is twice as old as Michael \n" ); document.write( "J=2*M [ this is your first equation ] \n" ); document.write( "--- \n" ); document.write( "The sum of their ages 3 years ago was 45 years \n" ); document.write( "J-3 is jean's age 3 years ago \n" ); document.write( "M-3 is Michaels age 3 years ago, so.... \n" ); document.write( "(J-3) + (M-3)=45 [ this is your second equation] \n" ); document.write( "--- \n" ); document.write( "simplify the second equation \n" ); document.write( "(J-3) + (M-3)=45 \n" ); document.write( "J+M-6=45 \n" ); document.write( "J+M=51\r \n" ); document.write( "\n" ); document.write( "--- \n" ); document.write( "So now you have two equations and 2 unknowns \n" ); document.write( "There are many ways to solve this, substittution, elimination, matrices, graphing, guessing, cramer method, etc...... \n" ); document.write( "--- \n" ); document.write( "Try subtitution since the first equation is already set to one of the variables \n" ); document.write( "J =2*M \n" ); document.write( "substitute this into the second equation \n" ); document.write( "J+M=51 \n" ); document.write( "(2*M)+M=51 \n" ); document.write( "3*M=51 \n" ); document.write( "M=51/3=17 \n" ); document.write( "--- \n" ); document.write( "So if M=17 and J=2*M then J=2*(17) =34 \n" ); document.write( "==== \n" ); document.write( "Check your answers\r \n" ); document.write( "\n" ); document.write( "go back to the original equations \n" ); document.write( "J=2M and (J-3) + (M-3)=45 to see if M=17 and J=34 are valid \n" ); document.write( " \n" ); document.write( " |