Three times the number of Doberman puppies is 3*20=<<3*20=60>>60
Five less than three times the number of Doberman puppies is 60-5=<<60-5=55>>55
Let's say the number of Schnauzers is s.
The difference between the number of Doberman puppies and the number of Schnauzers is s-20
Five less than three times the number of Doberman puppies plus the difference between the number of Doberman puppies and the number of Schnauzers is equal to 90, meaning 55+s-20=90.
The number of Schnauzers which is s+55-20=90
This evaluates to s+35=90
There are s=<<55=55>>55 Schnauzers
#### 55