Question 1042335
Let {{{ x }}} = the number of questions she got wrong
{{{ 43 / ( 43 + x ) = .86 }}}
{{{ 43 = .86*( 43 + x ) }}}
{{{ 43 = 36.98 + .86x }}}
{{{ .86x = 6.02 }}}
{{{ x = 7 }}}
She got 7 wrong
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check:
{{{ 43 / ( 43 + x ) = .86 }}}
{{{ 43 / ( 43 + 7 ) = .86 }}}
{{{ 43 / 50 = .86 }}}
{{{ 43 = .86*50 }}}
{{{ 43 = 43 }}}
OK