[Fred504610]

they are

x+y=4
x-y=8

and

2x+y=1
x=2y+8
help me this is very hard for me :confused:

[KISS]

The first is easy; just add them and get 2x=12;

From there it's easy to find x & y. Do you understand what I did?

2nd;

multiply the bottom by -2

2x+y=1
-2x-4y=-16

add

-3y=-15; take it from there?

[Fred504610]

The first is easy; just add them and get 2x=12;

From there it's easy to find x & y. Do you understand what I did?

2nd;

multiply the bottom by -2

2x+y=1
-2x-4y=-16

add

-3y=-15; take it from there?

Thank you :)

[ISneezeFunny]

x+y=4
x-y=8

first equation:

x + y = 4

x = 4 - y

plug it into second equation.

x - y = 8

(4 - y) - y = 8

4 - 2y = 8

-2y = 4

y = -2

now, plug y back into the first equation.

x+y=4

x + (-2) = 4

x - 2 = 4

x = 6

you can solve the next problem this way as well.

[Oconomowoc]

x+y=4
x-y=8

x+y=4
x-x+y=4-x
y=4-x

x-(4-x)=8
x-4+x=8
2x-4=8
2x-4+4=8+4
2x=12
2x/2=12/2
x=6

x-y=4
6+y=4
6-6+y=4-6
y=-2

answer
x+y=4 x=6,y=-2
6+-2=4
6-2=4
4=4
correct!