Question 927545
Let {{{ a }}} = $ / pound of cinnamon tea
Let {{{ b }}} = $ / pound of spice tea
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(1) {{{ ( 4a + 1*b ) / ( 4 + 1 ) = 12 }}}
(2) {{{ ( 1*a + 4b ) / ( 1 + 4 ) = 15 }}}
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(1) {{{ ( 4a + b ) / 5 = 12 }}}
(2) {{{ ( 1*a + 4b ) / 5 = 15 }}}
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(1) {{{ 4a + b = 60 }}}
(2) {{{ a + 4b = 75 }}}
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Multiply both sides of (1) by {{{ 4 }}}
and subtract (2) from (1)
(1) {{{ 16a + 4b = 240 }}}
(2) {{{ -a - 4b = -75 }}}
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{{{ 15a = 165 }}}
{{{ a = 11 }}}
and
(2) {{{ a + 4b = 75 }}}
(2) {{{ 11 + 4b = 75 }}}
(2) {{{ 4b = 64 }}}
(2) {{{ b = 16 }}}
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The cost / pound of the cinnamon 
tea is less than the spice tea