Question 1190535
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Let's multiply both sides of x-y=3 by 4
We should end up with 4x-4y=12


The original system of
{{{system(x-y=3,2x+4y=9)}}}
is equivalent to
{{{system(4x-4y=12,2x+4y=9)}}}


Notice how we have -4y and +4y from the first and second equations respectively. 
They add to 0y, aka 0. The y terms go away.


Let's add the terms straight down<ul><li>4x+2x becomes 6x</li><li>-4y+4y becomes 0y and goes away (hence the term "elimination")</li><li>12+9 becomes 21</li></ul>We're left with this equation: 6x = 21
Divide both sides by 6 to solve for x. You should get x = 21/6 = 7/2 = 3.5


Let's plug this into any equation involving x and y, and solve for y
x-y = 3
3.5-y = 3
-y = 3-3.5
-y = -0.5
y = 0.5
y = 1/2


Or,
2x+4y = 9
2(3.5)+4y = 9
7+4y = 9
4y = 9-7
4y = 2
y = 2/4
y = 1/2
y = 0.5



Answer in fraction form: x = 7/2 and y = 1/2
Answer in decimal form: x = 3.5 and y = 0.5
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