Question 956199
Let {{{ b }}} = number of boys and
{{{ g }}} = number of girls
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At the start,
{{{ b = g }}}
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After {{{ 16 }}} girls leave,
{{{ b = 5*( g - 16 ) }}}
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{{{ b = 5g - 80 }}}
{{{ 5g - b = 80 }}}
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Since {{{ b = g }}}
{{{ 5b - b = 80 }}}
{{{ 4b = 80 }}}
{{{ b = 20 }}}
and
{{{ g = 20 }}}
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20 girls attended at first
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check:
{{{ b = 5*( g - 16 ) }}}
{{{ 20 = 5*( 20 - 16 ) }}}
{{{ 20 = 5*4 }}}
{{{ 20 = 20 }}}
OK