Question 1137666
Let {{{ x }}} = number of psychology books sold
{{{ x - 47 }}} = number of sociology books sold
{{{ x + ( x - 47 ) = 479 }}}
{{{ 2x = 479 + 47 }}}
{{{ 2x = 526 }}}
{{{ x = 263 }}}
and
{{{ x - 47 = 263 - 47 }}}
{{{ x - 47 = 216 }}}
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263 psychology books were sold
216 sociology books were sold
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check:
{{{ 263 + 216 = 479 }}}
{{{ 479 = 479 }}}
OK