Answer :

when you divide 1722 by 6 you get 287 so it's not a repeating number so if you estimate 287 to 290 then you get 1740 so your answer is 287.
The answer was 287. But if you want to estimate. Estimating meaning calculate the answer as if you were to say I have 13 candy bars i wanted to give everyone of my 3 friends equal amounts without including yourself you would have to give everyone 4 candy bars and have one left over in which you could keep it for yourself or give everyone 4 pieces of your 12 piece candy bar. 
If your estimating that it would have to be 290 which is a reasonable answer because the 7 in the ones place is closer to 10 then 0