Step-by-step explanation:
as always in such problems, our first approach is to use for every sub-selection (in our case of 3 numbers) a mixture of smaller and larger numbers.
we have 3. 4, 5, 6, 7 available.
so, my first thoughts are "how about I try 3, 4 and 7" for one line of 3 numbers.
so, I would have a total 3+4+7 = 14
that leaves me with 5 and 6.
5+6 = 11
hmmm. what is missing to the previous total of 14 ? 3.
ha !
is there a "3" I can share with the other number line ? yes the other number line has a "3".
so, if I make 3 my center number, it applies to the total of both number lines.
4+3+7 = 14
5+3+6 = 14
and bang ! there you have your solution.
3 in the middle, 4 and 7 on the outside in one direction, and 5 and 6 on the outside in the other direction.
