Find the square root of 16 to get 4. A bulldog is 4. For the second line, 4xaxa=36. A is 3. So the white dog is 3. For the third line, 4x3=12. To get 72, you need to multiply by 6. So be black dog is 6. For the last line, 4+3+6=13. Hope this helps! ;)