According to Formula 2, the bus with a bear head =( 19-7)÷2=6.
According to Equation 3, Dr. Hat = 15-7-6=2.
Look at the last formula carefully. 1' s bear head has no doctor hat, and the two doctors in the middle are together, and the bus has no bear head.
Bear head without a doctor's hat =7-2=5
Bearingless bus =6-5= 1
Two overlapping doctor's hats =2+2=4
Finally, the formula is actually
5+4× 1=9
The final result is 9.