<PRE><B>Question 672830</B>
Let {{{ a }}} = bags of Doritos bought
Let {{{ b }}} = bags of Cheetos bought
given:
(1) {{{ a + b = 15 }}}
(2) {{{ 1.79a + 2.01b = 28.17 }}}
---------------------------
(2) {{{ 179a + 201b = 2817 }}}
Multiply both sides of (1) by {{{ 179 }}}
and subtract (1) from (2)
(2) {{{ 179a + 201b = 2817 }}}
(1) {{{ -179a - 179b = -2685 }}}
{{{ 22b = 132 }}}
{{{ b = 6 }}}
and
(1) {{{ a + 6 = 15 }}}
(1) {{{ a = 9 }}}
9 bags of Doritos were bought
6 bags of Cheetos were bought
check:
(2) {{{ 1.79*9 + 2.01*6 = 28.17 }}}
(2) {{{ 16.11 + 12.06 = 28.17 }}}
(2) {{{ 28.17 = 28.17 }}}
OK
</PRE>