Let us start with the schnauzers, the easiest one to imagine. Let us assume that there were x number of schnauzers.
Scottie's are 3 more than schnauzers. So their number is x+3
Wire haired terriers are 5 less than twice the number of schnauzers.
So their number is 2x -5 (2x for twice the number of schnauzers)
Now add all these numbers.
That is x + x+3 + 2x-5 = 4x -2
The total number of dogs, 78, is given in the question
Now we know that 4x -2 =78
4x = 78 +2
= 80
Therefore x = 80/4
= 20.
So there were 20 schnauzers, 23 Scottie’s and 35 wire haired terriers