Its really easy, the number is 4,175, right?
lets say ur trying to find the hundreds
4,175, the bolded number is your "check digit"
you then look to the number on its right, which would be 4,1<u>7</u>5 (underlined)
if its five or lower, round down (if it was lower then five then the answer would be 4,100)
if its six or higher, round up. (because it IS higher then 6, then the answer is 4,200)
its the same for the others too
Ten: 4,170
Hundred: 4,200
Thousand: 4,000
Have a luvly day