document.write( "Question 624391: select the set of equations that represent the following situation. Mary invested one amount at 10% simple interest, and a second amount at 3% interest, earning $21.72 in one year. If she had switched the amounts, she would have earned $15.07. What were the two amounts. \n" ); document.write( "

Algebra.Com's Answer #392712 by josmiceli(19441) $\"\"$ $\"About$

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$\"+.1a+%2B+.03b+=+21.72+\"$
\n" ); document.write( " $\"+.1b+%2B+.03a+=+15.07+\"$
\n" ); document.write( "-------------------
\n" ); document.write( "(1) $\"+10a+%2B+3b+=+2172+\"$
\n" ); document.write( "(2) $\"+10b+%2B+3a+=+1507+\"$
\n" ); document.write( "Multiply both sides of (1) by $\"+3+\"$
\n" ); document.write( "and both sides of (2) by $\"+10+\"$
\n" ); document.write( "(1) $\"+30a+%2B+9b+=+6516+\"$
\n" ); document.write( "(2) $\"+30a+%2B+100b+=+15070+\"$
\n" ); document.write( "Subtract (1) from (2)
\n" ); document.write( "(2) $\"+30a+%2B+100b+=+15070+\"$
\n" ); document.write( "(1) $\"+-30a+-+9b+=+-6516+\"$
\n" ); document.write( " $\"+91b+=+8554+\"$
\n" ); document.write( " $\"+b+=+94+\"$
\n" ); document.write( "Plug this result back into either equation
\n" ); document.write( "(2) $\"+10%2A94+%2B+3a+=+1507+\"$
\n" ); document.write( "(2) $\"+940+%2B+3a+=+1507+\"$
\n" ); document.write( "(2) $\"+3a+=+1507+-+940+\"$
\n" ); document.write( "(2) $\"+3a+=+567+\"$
\n" ); document.write( "(2) $\"+a+=+189+\"$
\n" ); document.write( "$189 was invested @ 10%
\n" ); document.write( "$94 was invested @ 3%
\n" ); document.write( "check:
\n" ); document.write( " $\"+.1b+%2B+.03a+=+15.07+\"$
\n" ); document.write( " $\"+.1%2A94+%2B+.03%2A189+=+15.07+\"$
\n" ); document.write( " $\"+9.4+%2B+5.67+=+15.07+\"$
\n" ); document.write( " $\"+15.07+=+15.07+\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );