Question 763951
With work problems, you must add their
RATES of working to get their RATE of working together
( sorry for shouting )
Tom's rate: 
( 1 job ) / ( 2 hrs )
Jerry's rate:
( 1 job ) / ( 3 hrs )
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Let {{{ t }}} = the time in hrs for them 
to finish the job working together
This rate is ( 1 job ) / ( t hrs )
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{{{ 1/2 + 1/3 = 1/t }}}
Multiply both sides by {{{ 6t }}}
{{{ 3t + 2t = 6 }}}
{{{ 5t = 6 }}}
{{{ t = 1.2 }}} hrs
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Every work problem is set up like this,
they will just be asking for different things