Question 392017
Let {{{h}}} = cost of 1 hamburger
Let {{{m}}} = cost of 1 glass of milk
given:
(1) {{{2h + 3m = 495}}} (in cents)
(2) {{{3h + 4m = 703}}}
Multiply both sides of (1) by {{{3}}},
multiply both sides of (2) by {{{2}}},
Then subtract (2) from (1)
(1) {{{6h + 9m = 1485}}} 
(2) {{{-6h - 8m = -1406}}}
{{{m = 79}}}
By substitution:
(1) {{{2h + 3*79 = 495}}}
{{{2h + 237 = 495}}}
{{{2h = 258}}}
{{{h = 129}}}
Hamburgers are $1.29 each and milk is $.79 a glass
check:
(2) {{{3h + 4m = 703}}}
{{{3*129 + 4*79 = 703}}}
{{{387 + 316 = 703}}}
{{{703 = 703}}}
OK