Having 3 tables same columns but with different values..result should be only same combination would be printed in the result set

example
table a

```
col x  col y
23     a01
23     a02
24     a11
25     a12

```

table b

```
col x  col y
23     a10
23     a02
24     a11
25     a12

```

table c

```
col x  col y
23     a01
23     a02
24     a11
25     a12

```

want the result as 

```
col x  col y
24     a11
25     a12

```

please help us to get the query