Question 1081489
{{{ 3.49x }}} is the amount that he paid
His change was {{{ 50 - 3.49x }}}
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(1)
{{{ 50 - 3.49x > 10 }}}
{{{ 50 > 10 + 3.49x }}}
{{{ 40 > 3.49x }}}
writing this in the other direction:
{{{ 3.49x < 40 }}}
{{{ x < 11.46 }}}
and
{{{ 50 - 3.49x < 20 }}}
{{{ 50 < 3.49x + 20 }}}
{{{ 30 < 3.49x }}}
write this the other way:
{{{ 3.49x > 30 }}}
{{{ x > 8.59 }}}
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Since he couldn't have a fraction of a box,
I would change these to:
{{{ x < 12 }}} ( note that {{{ 11 }}} is allowed }
{{{ x > 9 }}} ( note that  {{{ 8 }}} is NOT allowed )
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I can combine these as:
{{{ 9 < x < 12 }}}
You can get another opinion also ( if needed )