PLEASE ANSWER WITH SUBSTITUTION
9=3x-y
6x=3y+3

x = 8; y = 15

Step-by-step explanation:

First choose any one equation and isolate a variable of your choice

I will use the first equation and isolate variable y

9 = 3x - y

Add y to both sides to make it positive

y + 9 = 3x - y + y

Subtract both sides by 9 to isolate the variable y

y + 9 - 9 = 3y - 9

y = 3x - 9

Now that we know what expression is equal to y, we can substitute this value of y into the second equation

6x = 3(3x - 9) + 3

Use distributive property

6x = 9x - 27 + 3

Combine like terms

6x = 9x - 24

Subtract both sides by 9x

6x - 9x = 9x - 9x - 24

-3x = -24

Divide both sides by -3 to isolate the variable x

-3x ÷ -3 = -24 ÷ -3

x = 8

Plug this value of x into either equation

I will use the first equation because it is shorter

9 = 3(8) - y

9 = 24 - y

Add y to both sides to make y positive

y + 9 = 24 - y + y

y + 9 = 24

Subtract 9 from both sides to isolate the variable y

y + 9 - 9 = 24 - 9

y = 15