Question 912003
Let {{{ a }}} = pounds of type A needed
Let {{{ b }}} = pounds of type B needed
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(1) {{{ a = 2b }}}
(2) {{{ 5.95a + 7b = 56.7 }}}
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Substitute (1) into (2)
(2) {{{ 5.95*2b + 7b = 56.7 }}}
(2) {{{ 11.9b + 7b = 56.7 }}}
(2) {{{ 18.9b = 56.7 }}}
(2) {{{ b = 3 }}}
and, since
(1) {{{ a = 2b }}}
(1) {{{ a = 2*3 }}}
(1) {{{ a = 6 }}}
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6 pounds of type A is needed
3 pounds of type B is needed
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check:
(2) {{{ 5.95*6 + 7*3 = 56.7 }}}
(2) {{{ 35.7 + 21 = 56.7 }}}
(2) {{{ 56.7 = 56.7 }}}
OK