Answer:
y = -3x -16
Explanation:
For problems like this, I like to start with a variation of the point-slope form of the equation of a line:
y = m(x -h) +k . . . . . for a line with slope m through point (h, k)
For your given values, this is ...
y = -3(x +3) -7
y = -3x -9 -7 . . . . eliminate parentheses; next, combine terms
y = -3x -16