Answer:
3x - y = - 15
Step-by-step explanation:
The equation of a line in standard form is
Ax + By = C ( A is a positive integer and B, C are integers )
rearrange y = 3x + 15 into this form
subtract y from both sides
0 = 3x - y + 15 ( subtract 15 from both sides )
3x - y = - 15 ← in standard form