Question 1013311
Let {{{ a }}} = the cost of a box of pencils
Let {{{ b }}} = the cost of a box of pens
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(1) {{{ 3a + 2b = 6 }}}
(2) {{{ 2a + 4b = 8 }}}
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Multiply both sides of (1) by {{{ 2 }}}
and subtract (2) from (1)
(1) {{{ 6a + 4b = 12 }}}
(2) {{{ -2a - 4b = -8 }}}
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{{{ 4a = 4 }}}
{{{ a = 1 }}}
and
(1) {{{ 3a + 2b = 6 }}}
(1) {{{ 3*1 + 2b = 6 }}}
(1) {{{ 3 + 2b = 6 }}}
(1) {{{ 2b = 3 }}}
(1) {{{ b = 1.5 }}}
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A box of pencils costs $1
A box of pens costs $1.50
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check:
(2) {{{ 2a + 4b = 8 }}}
(2) {{{ a + 2b = 4 }}}
(2) {{{ 1 + 2*1.5 = 4 }}}
(2) {{{ 1 + 3 = 4 }}}
(2) {{{ 4 = 4 }}}
OK