Answer:
820
Step-by-step explanation:
Round to the nearest multiple of 10 (ex. 180, 190, 230, 240)
233 rounds to 230, going down.
189 rounds to to 190, going up.
402 rounds to 400, going down.
230 + 190 + 400 equals 820.
The question didn't specify, and the best way to estimate more accurately is by using multiples of 10.