Answer: 0.3
63/10 = 63 ÷ 10 = 6.3
If we want 6 we need to subtract a number (x) from 6.3
6.3 - x = 6
-x = 6 - 6.3
-x = -0.3
x = 0.3
So we need to subtract 0.3 from 6.3 to get 6.
Since this is a simple equation we could of just looked at it and saw that we need to subtract 0.3, but later when equations get more complicated this method will work better.
Hope this Helps! :)