Answer: 4x-5y+15 = 0
Work Shown:
y = (4/5)x + 3
5y = 4x + 15 ... multiply all terms by 5 to clear out the fraction
0 = 4x + 15 - 5y ... subtract 5y from both sides
4x-5y+15 = 0 .... rearrange terms
The equation is in standard form Ax+By+C = 0 where A = 4, B = -5, C = 15.
Some books use Ax+By = C to represent standard form. It's effectively the same thing just with C on the other side.