document.write( "Question 1137922: Can you please help me solve this problem: The sum of the ages of Mike and Dan is 20 years and four years dans age will be a 3/4 of mikes age how old is mike now? \n" ); document.write( "

Algebra.Com's Answer #755776 by math_helper(2461) $\"\"$ $\"About$

You can put this solution on YOUR website!


\n" );
document.write( "M = Mike's age
\n" );
document.write( "D = Dan's age
\r
\n" );
document.write( "\n" );
document.write( "M + D = 20               (eq 1)
\r
\n" );
document.write( "\n" );
document.write( "In four years:
\n" );
document.write( "(D + 4) = (3/4)(M + 4)   (eq 2)
\r
\n" );
document.write( "
\n" );
document.write( "\n" );
document.write( "You now have two equations in two unknowns.  One way to solve this system
\n" );
document.write( "is to substitute for M (M = 20 - D) from (eq 1) into (eq 2) to get a form of (eq 2) that only has variable D.   Then solve for D.\r
\n" );
document.write( "\n" );
document.write( "Once you have D, plug that value into (eq 1) to get M.  Be sure to check that the answers for D & M work in (eq 2). \r
\n" );
document.write( "\n" );
document.write( "     
\n" );
document.write( " \n" );
document.write( "

\n" );