In a certain code REINFORCE is written as ENOCRIFRE. How is ATTEMPT written in…

In a letter-coding question like this, the coded word is always formed by rearranging the exact same letters of the given word under one fixed position-based rule -- no letter is ever added, dropped, or changed. The first step is to discover that rule from the worked example, then apply it, position by position, to the new word.

1. Number the letters of REINFORCE by their position: R(1), E(2), I(3), N(4), F(5), O(6), R(7), C(8), E(9).

2. The first four letters of the code ENOCRIFRE -- E, N, O, C -- are exactly the letters standing at REINFORCE's even positions (2, 4, 6, 8), read left to right.

3. The remaining five letters of the code -- R, I, F, R, E -- are exactly the letters standing at REINFORCE's odd positions (1, 3, 5, 7, 9), again read left to right.

4. So the rule is: write the letters at the even positions first, in order, then the letters at the odd positions, in order.

5. Number the letters of ATTEMPT the same way: A(1), T(2), T(3), E(4), M(5), P(6), T(7).

6. Its even-position letters (2, 4, 6) are T, E, P.

7. Its odd-position letters (1, 3, 5, 7) are A, T, M, T.

8. Joining the even-position letters with the odd-position letters, in that order, gives the coded word.

As a check, the coded word must use exactly the seven letters of ATTEMPT -- one A, three T's, one E, one M, one P -- with nothing added, and splitting it back into its first three and last four letters must return precisely the even-position and odd-position letters of ATTEMPT; both checks hold.

So ATTEMPT is coded as TEPATMT.