Final answer:
To find x when y = 3, substitute the given x and y values into the equation y = 7 and solve for x.
Step-by-step explanation:
To find the value of x when y = 3, we can use the given equation y = 7 when x = 2. Since we know that y = 7 when x = 2, we can substitute the values into the equation to solve for x.
7 = 3x + 9
Subtracting 9 from both sides, we get:
-2 = 3x
Dividing both sides by 3, we find:
x = -2/3