document.write( "Question 1197758: A student bought a calculator and a textbook for a course in algebra. He told his friend that the total cost was $135 (without tax) and that the calculator cost $15 more than four times the cost of the textbook. What was the cost of each item? Let x= the cost of a calculator and y= the cost of the textbook. The corresponding modeling system is {x+y=135x=4y+15. Solve the system by using the method of substitution. \n" ); document.write( "

Algebra.Com's Answer #831165 by MathLover1(20850) $\"\"$ $\"About$

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The corresponding modeling system is \r
\n" ); document.write( "\n" ); document.write( " $\"x%2By=135\"$ .......eq..1
\n" ); document.write( " $\"x=4y%2B15\"$ ......eq.2
\n" ); document.write( "_________________________ \r
\n" ); document.write( "\n" ); document.write( " $\"x%2By=135\"$ .......eq..1, substitute $\"x\"$ from eq.2\r
\n" ); document.write( "\n" ); document.write( " $\"4y%2B15%2By=135\"$ .....solve for $\"y\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"5y=135-15\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"5y=120\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"y=24\"$ \r
\n" ); document.write( "\n" ); document.write( "go to\r
\n" ); document.write( "\n" ); document.write( " $\"x=4y%2B15\"$ ......eq.2, substitute $\"y\"$ value\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " $\"x=4%2A24%2B15\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"x=111\"$ \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "$ $\"111\"$ = the cost of a calculator and $ $\"24\"$ = the cost of the textbook\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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