Question 1090882
Let {{{ R[1] }}} = Ken's rate in chairs/hr
Let {{{ R[2] }}} = Ted's rate in chairs/hr
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Add their rate of making chairs to get their 
rate working together
(1) {{{ R[1] + R[2] = 1/3 }}}
(2) {{{ 2R[1] + R[2] = 1/2 }}}
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(1) {{{ R[1] + R[2] = 2/6 }}}
(2) {{{ 2R[1] + R[2] = 3/6 }}}
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Subtract (1) from (2)
{{{ R[1] = 1/6 }}}
Ken can make 1 chair in 6 hrs
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check:
(1) {{{ R[1] + R[2] = 1/3 }}}
(1) {{{ 1/6 + R[2] = 2/6 }}}
(1) {{{ R[2] = 1/6 }}}
and
(2) {{{ 2R[1] + R[2] = 1/2 }}}
(2) {{{ 2*( 1/6 ) + R[2] = 3/6 }}}
(2) {{{ R[2] = 3/6 - 2/6 }}}
(2) {{{ R[2] = 1/6 }}}
OK