x = 4

3x + y = 9

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1 answer

To solve for $y$ in the equation $3 x + y = 9$ given that $x = 4$ , we can substitute $x$ into the equation:

$3 (4) + y = 9$

Calculating $3 (4)$ :

$12 + y = 9$

Next, we isolate $y$ by subtracting 12 from both sides:

$y = 9 - 12$ $y = - 3$

Therefore, the solution is $(x, y) = (4, - 3)$ .

So, the final answer is $(4, - 3)$ .