Three different whole numbers add up to 31.
the first number is multiple of 3
the second number is multiple of 4
the third number is multiple of 5.
what could the numbers

Let's find the least possibilities:

First number: 6
Second number: 8
Third number: 10

6 + 8 + 10 = 24

Now we can see that we are still missing 31 - 24 = 7.

7 can be gained by adding 3 and 4, so:

First number: 6 + 3 = 9
Second number: 8 + 4 = 12
Third number: 10

9 + 12 + 10 = 31