Answer:
let x be the number of cats and y be the number of dogs:
x + y = 40
4x + 4y = 160
If you divide both sides of the second equation by 4, you will be left with:
x + y = 40
Then, subtract both equations:
x + y =40
- (x + y = 40)
0 = 0
Since you have a number = a number, there are infinite solutions.