Question 1008186
Let {{{ x }}} = price of a tuna sandwich
Let {{{ y }}} = price of a turkey sandwich
--------------------------------
(1) {{{ 6x + 6y = 30 }}}
(2) {{{ 4x + 8y = 30.6 }}}
---------------------
(1) {{{ x + y = 5 }}}
---------------------
(2) {{{ 40x + 80y = 306 }}}
(2) {{{ 20x + 40y = 153 }}}
---------------------
Multiply both sides of (1) by {{{ 20 }}}
and subtract (1) from (2)
(2) {{{ 20x + 40y = 153 }}}
(1) {{{ -20x - 20y = -100 }}}
----------------------
{{{ 20y = 53 }}}
{{{ y = 2.65 }}}
and
(1) {{{ x + y = 5 }}}
(1) {{{ x + 2.65 = 5 }}}
(1) {{{ x = 2.35 }}}
-----------------
A tuna sandwich costs $2.35
check:
(2) {{{ 4x + 8y = 30.6 }}}
(2) {{{ 4*2.35 + 8*2.65 = 30.6 }}}
(2) {{{ 9.4 + 21.2 = 30.6 }}}
(2) {{{ 30.6 = 30.6 }}}
OK