Answer:
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 <em>2 × 3 = 6. </em>
If we know that Billy has 8 animals, then we also know that Milly must have 9 animals, as <em>17 - 8 = 9.</em>
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.
<em>9 ÷ 3 = 3.</em>
This tells us Milly has just 3 llamas, because 3 is one group of 9, and <em>3 × 2 = 6</em>, because she has twice the amount of lambs.
<u>Billy has 2 lambs and 6 llamas.</u>
<u>Milly has 6 lambs and 3 llamas. </u>
The amount of lambs is irrelevant to our final answer, so we can disregard them and do a final sum of <em>6 + 3 = 9</em>, which gives us our answer.