If the number of pythons is three times the number of boa constrictors, then there are 3*40 = <<3*40=120>>120 pythons
Together, the number of pythons and boa constrictors is 120+40 = <<120+40=160>>160
If there are 200 snakes in the park, the number of rattlesnakes is 200-160 = <<200-160=40>>40
#### 40