Question 186265
Let {{{g}}}= pounds of green tea needed
Let {{{w}}}= pounds of white tea needed
given:
(1) {{{g + w = 10}}} lb
{{{4g + 2.75w = 3.5*10}}} dollars
(2) {{{4g + 2.75w = 35}}}
Multiply both sides of (1) by {{{4}}} and 
subtract (2) from (1)
(1) {{{4g + 4w = 40}}}
(2) {{{-4g - 2.75w = -35}}}
(3) {{{1.25w = 5}}}
(3) {{{w = 4}}}
and
(1) {{{g + w = 10}}}
(1) {{{g + 4 = 10}}}
(1) {{{g = 6}}}
4 pounds of white tea and 6 pounds of green tea are needed