Let cats be "x" and dogs be "y"
80 animals at max, so we can write:
[tex]x+y\leq80[/tex]Shelter has monthly budget of 900 max.
Cat, c, needs 10 for a month, and
Dog, d, needs 20 for a month,
We can write:
[tex]10x+20y\leq900[/tex]Now, we graph the equation:
x + y = 80
10x + 20 y = 900
The solution set is the area below (since less than or equal to) both the graphs.
The graph is shown below: