$947.50
 - $189.50
_________
$758.00
So, to do this first we start at the far right and go to the left.
   $947.50 - $189.50_________
   $      .00
0-0= 0
5-5= 0
You then bring down the decimal.
   $947.50 - $189.50_________
    $   8 .00
Because you cannot subtract 9 from 7, you borrow one from the number to the left of it and 7 turns into a 17 as 4 turns into a 3. So then, 17-9=8. 
         17
   $93-7-.50         -7- = This means the 7 has been canceled out and turned  - $189.50                        into the 17 above _________         8 .00
This happens again with subtracting 3 from 8 in which you take one from the number beside which happens to be 9 and make it 8. 
          17
   $8-3--7-.50         -7- and -3- = This means the 7 has been canceled out                                                         and turned into the 17 above 
  - $189.50                        _________    $ 58 .00
So then, 13-8=5. Finally 8-1= 7
   $947.50
 - $189.50
_________
$758.00