Supposed to find the solution using the method of subsititution, but both equations equal y

here's the equations, and i'm supposed to solve systems by subsititution, how do i do this?

y=7x+10
y=6x+9

how do i solve this?
and here's another too that aren't equal to y, but x. help with these too!:) thank you!!!

-x-4y=7
7x+6y=17

For the y in the first equation, you substitute the value of y in the second equation

top pair:

y = 7x + 10
becomes
6x + 9 = 7x + 10
subtract 6x from both sides
9 = x + 10
subtract 10 from both sides
-1 = x

---

In the second one, you could take the top equation

-x - 4y = 7
-7 - 4y = x

use that x in the second equation:
7(-7 - 4y) + 6y = 17
Then solve for y

Once you have y, use it in the original equations to find the value of x.

7x+10=6x+9 whatever you do to one side, you must do to the other
x+10=9 subtract 6x from both sides
x=-1 -1 plus 10 equals 9
y= 3 plug -1 back into equation


All you do is make the equation equal to y

-x-4y=7 add x to both sides
-4y=7+x divide everything by -4
y=-1 3/4-1/4x

Plug back into equation

7x+6(-1.75-.25x)=17
7x+-10.5-1.5x=17
5.5x-10.5=17
x=5

y = 7x +10, so replace y in the second equation with 7x+10 =>
7x+10 = 6x+9
7x-6x = 9-10
x = -1

-x-4y=7
add x to both sides
-4y = 7+x
subtract 7 from both sides
x = -4y-7
Now put that into the second equation
7x+6y=17
7(-4y-7) + 6y = 17
-28y-49+6y = 17
-22y = 17+49 =66
y = -3

Well, then:

7x + 10 = 6x + 9

rearrange so that one side has all the x terms, and the other the non-x terms
7x - 6x = 9 - 10

Simplify and you get:
x = -1