Question 1105045
Let {{{ a }}} = the cost of 1 hamburger
Let {{{ b }}} = the cost of 1 soda
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(1) {{{ 7a + 3b = 19 }}}
(2) {{{ 8a + 2b = 19.5 }}}
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(1) {{{ 7a + 3b = 19 }}}
(2) {{{ 80a + 20b = 195 }}}
(2) {{{ 16a + 4b = 39 }}}
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Multiply both sides of (1) by {{{ 4 }}}
Multiply both sides of (2) by {{{ 3 }}}
Then subtract (1) from (2)
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(2) {{{ 48a + 12b = 117 }}}
(1) {{{ -28a - 12b = -76 }}}
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{{{ 20a = 41 }}}
{{{ a = 41/20 }}}
and
(1) {{{ 7*(41/20) + 3b = 19 }}}
(1) {{{ 287 + 60b = 380 }}}
(1) {{{ 60b = 93 }}}
(1) {{{ b = 93/60 }}}
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1 hamburger and 1 soda  = 
{{{ a + b = 41/20 + 93/60 }}}
{{{ 123/60 + 41/60 = 164/60 
{{{ 164/60 = 2 + 44/60 }}}
{{{ 2 + 44/60 = 2 + 11/15 }}}
Change from $5 is {{{ 2 + 4/15 }}}
{{{ 4/15 = .27 }}}
$2.27 is the change from a $5 bill
check the math!