Math Method..solve it please

Can someone solve me these 2 equations in Algebraic Method (Substitution) and Elimination Method (Addition)? please show your solution please clearly?....

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

2.) 3x - y = 15
2x + y = 6


Thanks... 15 points....

Substitution; solve for 1 variable in 1 equation then 'substitute' or plug it in for that variable in the other equation to solve.

1) x - y = -5 ;(+y)
x = y - 5

x + 2y = 7 ; (substitute y-5 for x)
(y - 5) +2y = 7
3y - 5 = 7 ;(+5)
3y = 12 ;(/3)
y = 4

x - y = -5 ; (substitute 4 for y)
x - (4) = -5 ; (+4)
x = -1

(-1,4)

2) 3x - y =15 ; (+y,-15)
y = 3x - 15

2x + y = 6 ; (substitute 3x - 15 for y)
2x + (3x - 15) = 6
5x -15 = 6 ;(+15)
5x = 21 ; (/5)
x = 21/5

3x - y = 15 ; (substitute 21/5 for x)
3(21/5) - y = 15
63/5 - y = 15 ;(+y,-15)
y = -12/5

(21/5, -12/5)

Elimination adding the equations to 'eliminate' a variable and leave only one to work with.

1)x + 2y = 7
x - y = -5 ; (*2,so we can cancel y when we add)

x + 2y = 7
2x -2y = -10 ; (add the equations)

3x = -3 (/3)
x = -1

x + 2y = 7
x - y = -5 ; (*-1, to make the x's opposite so they'll cancel when we add them)

-x - 2y = -7
x - y = -5 ; (add the equations)

-3y = -12 ; (/-3)
y = 4

(-1,4)

2)3x - y = 15
2x + y = 6 ; (y's are opposite so add the equations)

5x = 21 ; (/5)
x = 21/5

3x - y = 15 ;(*-2)
2x + y = 6 ;(*3,to make x's opposite)

-6x + 2y = -30
6x + 3y = 18 ; (add the equations)

5y = -12 ; (/5)
y = -12/5

(21/5,-12/5)

also it helps to plug your answers into both your equations to see if they work afterwards (these do I checked)
hope this helps

x + 2y = 7 ---- x+2y=7 x+2y=7
x - y = -5 ------2(x-y=-5) 2x-2y=-10 so ready for elimination now add two equation and have