Solve by elimination?

Question

x + 9y = 90

- x + 3y = 18

Answer 1

Elimination by addition method

x + 9y = 90- - - - - -Equation 1
-x + 3y = 18- - - - -Equation 2
- - - - - - - - -
12y = 108

12y / 12 = 108 / 12

y = 108/12

y = 9

Insert the y value into equation 1
- - - - - - - -

x + 9y = 90

x + 9(9) = 90

x + 81 = 90

Transpose 81

x + 81 - 81 = 90 - 81

x = 90 - 81

x = 9

Insert the x value into equation 1
- - - - - - - -

Check for equation 1

x + 9y = 90

9 + 9(9) = 90

9 + 81 = 90

90 = 90
- - - - - - -

Check for equation 2

- x + 3y = 18

- 9 + 3(9) = 18

- 9 + 27 = 18

18 = 18

- - - - - - - -

Both equations balance

The solution set is { 9, 9 }

- - - - - - - - -s-

Answer 2

The "Elimination" method requires that you get one variable in one equation to be equal in magnitude but opposite in sign to the same variable in the other equation. Once this is achieved, simply add one equation to the other. One variable gets eliminated, and you can then solve for the other one.

For your equations, we already have the "equal in magnitude, opposite in sign" condition. I will therefore add.
x+9y=90
-x+3y=18
_______
....12y=108
y=9
Having added -x+3y to the left side of x+9y=90, I should have added -x+3y to the right side too. I did!.
Since -x+3y is equal to 18, I added 18 instead.
Knowing now that y=9, I shall substitute 9 for y in either one of the original equations to find x
x+9y=90
x+9(9)=90
x+81=90
X=90-81
x=9
And we're done. x=9,y=9

Answer 3

X+9y=90
X+9y Divided by 9= 90 divided by 9
X+y=10

-X+3y=18
-X+3y Divided by 3=18 divided by 3
-X+y=6
X-y= -6

Answer 4

x+9y=90
-x+3y=18
+ -
-----------
12y=108
y=108/12
y=9

so x+9y=90
x=90-9(9)
=90-81
=9
so x,y =9,9
=

Answer 5

add the 2 equations to get 0x +12y = 108
y=9
if y=9 then x + 9x9 = 90 and c=90-81=9
x=9, y=9

Answer 6

x+9y=90-------------------(1)
&-x+3y=18-----------------(2)
adding we get,
12y=108 or y=9
multiplying (2) with 3,we have
-3x+9y=54------------------(3)
subtracting (3)from (1),we have
4x=36 or x=9,so the solution is(9,9) ans

Answer 7

x + 9y = 90
-x + 3y = 18
-----------------
0x + 12y = 108

y= 9 ... Plug it back in

x + 9(9) = 90
x+ 81 = 90
x= 9

(9,9)

Answer 8

add the two equations together
12y=108
y=9
x=9