Let’s solve the following math problem. Each rabbit has 4 feets and each duck has 2 feets. If there are in total 25 heads and 88 feets, how many rabbits and how many ducks are there?

We can use equations to solve this problem. Let the number of ducks be X and the number of rabbits be Y. We have 
X+Y = 25 (1) 
2X + 4Y = 88 (2). 
From the first equation, we know that X = 25-Y and we can substitute this into the second equation (2), and we get
2(25-Y) + 4Y = 88
Which can be simplified to 50 + 2Y = 88 and we have Y = 19.
We substitute the value into (1), we will then get X = 6. 
There are 6 ducks and 19 rabbits!