Billy has three times as many llamas as lambs.

Milly has twice as many lambs as llamas.

They have 17 animals in total.

How many of the animals are llamas?

Billy: Has 4 lots of animals

Milly: Has 3 lots of animals

17 animals in total means that Billy must have 4 lots of 2 (8 animals) and Milly must have 3 lots of 3 (9 animals) So Billy has 6 llamas and Milly has 3, giving 9 llamas in total

There are 9 llamas.

Step-by-step explanation:

For Billy, we have to find a number that is divisible by four, because he has one group of lambs, and 3 times as many llamas, which gives us 4 groups altogether. The number must be below 10 in order to not go above 17 when Milly's number of animals are included, but above 4 itself in order to reach the target of 17 in the first place.

As you can guess, the only number that fits all the criteria is 8. It's divisible by 4 and below 10, but above 4 itself.

If Billy has three times as many llamas as lambs, then he must have 2 lambs, and 6 llamas, as 2 * 3 = 6.

If we know that Billy has 8 animals, then we also know that Milly must have 9 animals, as 17 - 8 = 9.

We also know that Milly has 3 groups of animals; one group of llamas, and two groups of lambs, meaning we divide the number of animals she has by 3.

9 : 3 = 3.

This tells us Milly has just 3 llamas, because 3 is one group of 9, and 3 * 2 = 6, because she has twice the amount of lambs.

Billy has 2 lambs and 6 llamas.

Milly has 6 lambs and 3 llamas.

The amount of lambs is irrelevant to our final answer, so we can disregard them and do a final sum of 6 + 3 = 9, which gives us our answer.