The sum of two numbers is 5.036. one number has a 4 in the tenths place and 7 in the thousandths place. the other number has a 1 in the ones place and an 2 in the hundredths place. what are the two numbers.

   1.x2x
 +x.4x7
   5.036  (sorry the underline function is no longer available)

In the thousandth column we have x +7 and we wind up with a 6 in that column.
 Since 7 is already more than 6 that means the only number that will work is 9 and there will be a carry of one into the hundredths place.

  1.x29
+x.4x7
  5.036

Now let's look at the tenths column.  2 becomes 3 in the answer and there was a carry of 1 from the thousandths so the other number must be a zero
   1.x29
+ x.407
   5.036   Now I need a number that goes with 4 and puts a zero in the answer.
                That number has to be 6 and does cause a carry of one into the ones
                 place

  1.629
+x.407
  5.036  

Finally (remembering there is a carry of one in the ones place)  I have two (1 + 1 carried) toward my five in the answer.  I need three more.

Here is the final example:
    1.629
  +3.407
    5.036