Question 1157699
Their rate working together is 
[ 1 job done ] / [ 2 hrs ] = {{{ 1/2 }}}
Let {{{ t }}} = time in hrs for Pam to
mow the lawn alone
Pam's rate is {{{ 1/t }}}
John's rate is {{{ 1/(2t) }}}
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Add their rates to get the rate working together
{{{ 1/t + 1/(2t) = 1/2 }}}
Multiply both sides by {{{ 2t }}}
{{{ 2 + 1 = t }}}
{{{ t = 3 }}} hrs
Pam takes 3 hrs working alone
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check:
{{{ 1/t + 1/(2t) = 1/2 }}}
{{{ 1/3 + 1/6 = 1/2 }}}
{{{ 2/6 + 1/6 = 3/6 }}}
OK