336
First, add the digits other than the units, 90 + 230 = 320. Remember that for a moment. Now, add the one's digits, 7 + 9 = 16. Now, add the 16 to the 320 to get 336. ---- Alternately, subtract 3 from 239 and give it to 97, so we have 100 + 236 = 336.