solve by addition?

Question

Solve the system by addition.
2x – 4y = 7
4x + 2y = 9

Answer 1

2x-4y=7
4x+2y=9 (Multiply by 2)

2x-4y=7
8x=4y=18 (y's cancel out)

10x=25

x=2.5

SUBSTITUTE:

2(2.5)-4y=7
5-4y=7
-4y=-2

y=0.5

Answer 2

alright I believe in order to solve this you want to get it so that either x or y cancels out when you add the equations together. An easy one to do is to multiply the bottom equation by 2 because then -4y would cancel with 4y and you'd only have one variable in the equation.
2x-4y=7
2(4x+2y=9)

2x - 4y = 7
+ 8x+ 4y=18
=10x+ 0y=25
Then you can solve for x and then plug x into one of the equations and solve for y.

Answer 3

Multiply the first equation by -2 to get -4x + 8y = -14.

Now ADD the two equations together. The x terms add up to zero, leaving

10y = -5, or y = -1/2

Multiply the second equation by 2 to get 8x + 4y = 18

Now ADD the two equations together. The y terms add up to zero leaving:

10x = 25, x = 2.5

Answer 4

Work one problem at a time
2x-4y = 7
2x = 7+4y
x = 3.5+2y
(you cannot break down X any further, so apply it to the next one)
LIKE THIS
4x+2y = 9
4(3.5+2y)+2y = 9
14+8y+2y = 9
14+10y = 9
10y = -5
y = -1/2 (negative)
(this one is broken down completely, take the answer and apply it to the first equation)
LIKE THIS
2x - 4(-1/2) = 7
2x - (-2) =7
2x +2 = 7
2x = 5
x = 2.5
(now you have your final answer for X)
THEREFORE
X = 2.5
Y = -1/2

Plug in the numbers into your beginning equations to verify

Answer 5

2x-4y=7
2(4x+2y)=2(9)
8x+4y = 18
10x=25
x= 2.5
2(2.5) -4y = 7
-4y=2
y= -.5

Answer 6

2x-4y=7
8x+4y=18
10x=25
x=2.5
sub
5-4y=7
-4y=2
y=-0.5

Answer 7

tHere has to be at least one variable that is known to find the final answer, so you have both of those equations as the answer, I believe.