At the zoo, Peter saw 9 animals. Some are kangaroos and some are elephants. There are 30 legs in all. How many of each animal are there?

6 elephants and 3 kangaroos in the zoo.

Step-by-step explanation:

Number of animals = 9

Number of legs seen = 30

But an elephant has 4 legs, while a kangaroo has 2 legs.

Let the number of elephant be represented by E, and the number of kangaroo by K.

So that,

E + K = 9 1

4E + 2K = 30 2

Multiply equation 1 by 2 to have

2E + 2K = 18 3

Subtract equation 3 from 1

2E = 12

E = 6

Substitute the value of E in equation 1

E + K = 9

6 + K = 9

k = 3

Thus, there were 6 elephants and 3 kangaroos in the zoo.