Question 587657
Let {{{ x }}} = number of black mollies at start
given:
{{{ 144/x = 3/5 }}}
{{{ 144*5 = 3x }}}
{{{ x = 720/3 }}}
{{{ x = 240 }}}
The number of the black mollies did not change.
let {{{ y }}} = number of guppies after some had died
{{{ y / 240 = 3/8 }}}
{{{ 8y = 3*240 }}}
{{{ 8y = 720 }}}
{{{ y = 720/8 }}}
{{{ y = 90 }}}
{{{ 144 - 90 = 54 }}}
54 guppies died