what is d answer for x + 2y = 7? and x - y = 4? pki-answer plssss.. i need it NOW!!!?

Simply subtract your two given equations as follows:

x + 2y = 7
x - y = 4
___________

3y = 3

y = 1

and knowing what "y" is, you can substitute this is either of the above equations and solve for "x" as in,

x - 1 = 4

and solving for "x",

x = 4 + 1

x = 5

for the 1st one y=7/2 - x
the 2nd one: y= -4 +x

x + 2y = 7
x - y = 4

x + 2y = 7
x = 7 - 2y

x - y = 4
(7 - 2y) - y = 4
7 - 2y - y = 4
-2y - y = 4 - 7
-3y = -3
y = -3/-3
y = 1

x + 2y = 7
x + 2(1) = 7
x + 2 = 7
x = 7 - 2
x = 5

∴ x = 5 , y = 1

Class assignment? Don't worry, the question isn't so difficult once you're taught the basics. I'll give you the answer, though.

First, set up a system of equations:
x + 2y = 7
x - y = 4

Then you subtract the bottom equation from the top in order to remove x and get y by itself:

(x + 2y = 7)
- (x - y = 4)

equals: 3y = 3

Divide each side by three

3y/3 = y
3/3 = 1

y = 1

Substitute the numeric value of y (1) into any of the two original equations in order to find out x:

x + 2(1) = 7
x + 2 = 7
or
x - (1) = 4
x - 1 = 4

Solve for x.

x + 2 = 7
x = 5
or
x-1 = 4
x = 5

ultimately the answer is (x = 5; y = 1).

I hope it's clear enough for you to understand.

x=4+y

(4+y)+2y=7
4+3y=7
3y=3
y=1

x-y=4
x-1=4
x=5

x + 2y = 7
x - y = 4

Subtract the second equation from the first, then solve for y.
Once you have y, add four to it and you have x.