First find the total number of inches of nylon used for the dog collars: 18 inches/dog collar * 9 dog collars = 162 inches
Then find the total number of inches of nylon used for the cat collars: 10 inches/cat collar * 3 cat collars = 30 inches
Then add the nylon needed for the cat and dog collars to find the total amount needed: 162 inches + 30 inches = <<162+30=192>>192 inches
#### 192