Y=-3x
y=6x-9 in substitution method

The two equations given in the question are
y = - 3x
And
y = 6x - 9
Let us now substitute the value of y from the first equation to the second equation, we get
y = 6x - 9
- 3x = 6x - 9
-3x - 6x = - 9
- 9x = - 9
Multiplying both sides of the equation by -1 we get
9x = 9
x = 9/9
   = 1
Now let us put the value of x in the first equation, we get
y = - 3x
   = - (3 * 1)
   = - 3

Hi

y = -3x
y = 6x-9 ⇒

y = 6x-9 ⇒ -3x = 6x-9 ⇒ -3x-6x = -9 ⇒ -9x = -9 ⇒ x = -9/-9 ⇒ x = 1

y = -3x
y = -3(1)
y = -3

x = 1 and y = -3