Question 1135250
Let {{{ t }}} = the time in minutes 
to screen-print 1 shirt
Let {{{ n }}} = number of shirts screen-printed
in {{{ t }}} minutes
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In terms of units:
[ total minutes ] / [ minutes / shirt ] = [ number of shirts ]
{{{ n = ( t-16 )/(4/3)  }}}
{{{ n = ( 3/4 )*( t - 16 ) }}}
{{{ n = (3/4)*t - 12 }}}
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{{{ n = 12 }}}
{{{ 12 = (3/4)*t - 12 }}}
{{{ ( 3/4 )*t = 24 }}}
{{{ 3t = 96 }}}
{{{ t = 32 }}}
It takes 32 min
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check:
{{{ 32 - 16 = 16 }}} total min printing
[ min/shirt ] x [ number of shirts ] = [ total min ]
{{{ ( 4/3)*12 = 16 }}}
OK