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?
Let’s use equations to solve it! 
Let the number of ducks be X and the number of rabbits be Y.
We have X + Y = 25 and 2X + 4Y = 88.
Simplifying the first equation, we get Y = 25 - X
Substitute that in the second equation, we will get 2X + 4(25-X) = 88,
Thus 100 - 2X = 88
Which means 2X = 100 – 88 = 12, thus X = 6.
We substitute back into the first equation, we have Y = 25 - 6 = 19.
There are 6 ducks and 19 rabbits!