Question 687626
I assume that the job was completed 
after they did their work.
So, each one contributed a fraction and
the 2 fractions should add up to 1.
{{{ (x + 2) /4 + (x + 3) /6 = 1 }}}
Multiply both sides by {{{ 12 }}}
{{{ 3*( x + 2 ) + 2*( x + 3 ) = 12 }}}
{{{ 3x + 6 + 2x + 6 = 12 }}}
{{{ 5x = 0 }}}
{{{ x = 0 }}}
{{{ ( x+2 )/4 = ( 0+2 )/4 }}}
{{{ ( 0 + 2 )/4 = 1/2 }}}
and
{{{ ( x + 3 )/6 = ( 0 + 3 )/6 }}}
{{{ ( 0 + 3 ) / 6 = 1/2 }}}
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I get they both did 1/2 of the job. 
Check my work, though