Explanation:
In the equation 3x + y = 5, we can rearrange it to slope-intercept form:
y = -3x + 5
Now, we can see that the slope of this line is -3 (the coefficient of x).
In the equation y = 3x + 9, the slope is 3 (the coefficient of x).
For two lines to be parallel, their slopes must be equal. In this case, the slope of the first line is -3, and the slope of the second line is 3. These slopes are not equal; they are negatives of each other. Therefore, the two lines are not parallel.