Thanks for the question. If you want to express the angle in "standard position", which seems to be what you're after with adding something to 270 degrees, you would need to add (90-47.4) to 270. 90-47.4 gives the bit of angle between the terminal arm and the negative y-axis. This standard position angle (312.6 degrees) would be a fine answer as well.
Keep in mind that calculators usually give the "reference angle" (see https://brilliant.org/wiki/reference-angle/) which, in this case, is 47.4 degrees, and because of the way the angle is drawn, this angle is below the negative x-axis.