document.write( "Question 961797: A student receives grades of 63, 77, and 89 on her first three algebra tests. What grade does she need on her fourth (and final) test in order to have an average of 80 (and get a B in the course)? \n" ); document.write( "

Algebra.Com's Answer #587664 by josmiceli(19441) $\"\"$ $\"About$

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[ average ] = { sum of test scores ] / [ number of tests ]
\n" ); document.write( "Let $\"+x+\"$ = her score on the 4th test
\n" ); document.write( " $\"+80+=+%28+63+%2B+77+%2B+89+%2B+x+%29+%2F+4+\"$
\n" ); document.write( " $\"+80+=+%28+229+%2B+x+%29+%2F+4+\"$
\n" ); document.write( " $\"+x+%2B+229+=+320+\"$
\n" ); document.write( " $\"+x+=+91+\"$
\n" ); document.write( "She has to get a 91 on the 4th test
\n" ); document.write( " \n" ); document.write( "

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