``````function pairwise(arr, arg) {
return arg;
}

pairwise([1,4,2,3,0,5], 7);
``````

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https://www.freecodecamp.org/challenges/pairwise

What in particular about the instructions and example don’t you understand?

You might find it helpful to use pen and paper when looking at the example - this question took me a while to understand too

And then what i do?
i don’t understand what to do with numbers and pairwise

Let’s talk through the example then:

`pairwise([7, 9, 11, 13, 15], 20)`

When we call this function, we have the array `arr` with elements `[7, 9, 11, 13, 15]` in it. We want to find pairs of elements that add up to `20`. The number `20` is stored in the variable `arg`.

We need to find pairs of numbers in that array that add up to `20`, so let’s start by looking at the first value, `7`. We’d need `13` to be in the list to have a pair, which we do! So `[7, 13]` is a pair that adds to what we want!

`7` was found at the start of `arr` so its index is `0`. `13` is found in `arr` so its index is `3`. The question wants the sum of indices for the pair, so that’s `0 + 3` which is `3`.

Repeating the above for the other numbers shows us that there is another pair of elements in `arr` that add up to `arg`. `9 + 11` is also `20`, and we find them at indices `1` and `2`. Their index sum is `3` also.

Because we had multiple pairs, we add up their index sums, so `3 + 3` is `6`, which is the final answer we’re looking for, so we `return` it.

Ok I try it and if don’t do it i question you

i tried last night but I don’t managed.Can you help me more??

Which part did you get up to?

I’ll give a few hints now as to one way you can break up the problem into smaller ones. (this isn’t the most efficient way to solve the problem, but it’s good enough and conceptually the most simple)

1. Write a function that finds the first index of a given number. We only want the first index of a given number if it appears multiple times, because of something the question asks. Hint: you can use `.indexOf()` for this

2. Write a function that finds the difference between the value we want, and a given value. e.g. if we want a sum of 20, and we put in the number 3 and the function returns 17.

3. Write a function that looks at the array `arr`, and for each value in `arr` uses function 2 to find the difference, and then function 1 to find the index of the difference.

If in function 3 the difference can’t be found, move on to the next element. If in function 3 the difference is found, then store the sum of the indices somewhere.

Let me know if there’s something you don’t understand written here

Reply back and post your code, so we can see what you have tried so far.

To enter a code block into the forum, precede it with a line of three backticks and follow it with a line of three backticks to make easier to read. See this post to find the backtick on your keyboard. The “preformatted text” tool in the editor (`</>`) will also add backticks around text. thank you but i did it sorry for destraction