When you have a table like this given

          | O | A | B |AB |
---------------------------
Type Rh+  |37 |36 | 9 | 3 |
Type Rh-  | 7 | 6 | 1 | 1 |

Always add on a column of totals on the right and
a row of totals on the bottom, like this, and add
the numbers across and down, and the total of the
new column should equal the total of the new row.
 
          | O | A | B |AB |Totals|
---------------------------------|
Type Rh+  |37 |36 | 9 | 3 |  85  |
Type Rh-  | 7 | 6 | 1 | 1 |  15  |
----------------------------------
Totals    |44 |42 |10 | 4 | 100  |

So we add all those that are either in the "Type Rh+" row or
in the "O" column. That is, the red ones below fit the property
of being in one OR the other category:

          | O | A | B |AB |Totals|
---------------------------------|
Type Rh+  |37 |36 | 9 | 3 |  85  |
Type Rh-  | 7 | 6 | 1 | 1 |  15  |
----------------------------------
Totals    |44 |42 |10 | 4 | 100  |

That's 37 + 36 + 9 + 3 + 7 = 92

It's that many, 92, out of 100, so the answer is 



[Notice that we can't just add the "Rh+" row, 85, to the "O" column to get 44+85,
which is too many, 129, because that would be adding the 37 twice, unless we
then subtracted the 37 and then got 129-37 which is 92.]  

Edwin