Cost of each pound of dog food = $2 .
Total cost of 9 pounds of dog food = 9 * 2 = $18.
Let us assume number of treats she can buy = t.
Cost of each treat = $1.
Cost of t number of treats = 1*t = 1t .
Total money Cara has = $25.
We can setup an inequality as,
Total cost of dog food + total cost of t number of treats ≤ 25.
18 + 1t ≤ 25.
Subtracting 18 from both sides, we get
18 + 1t -18 ≤ 25-18.
1t ≤ 7 or t ≤ 7.
So, she can purchase 7 or less treats.