A Word Sum Puzzle is a word game

Word game

Word games and puzzles are spoken or board games often designed to test ability with language or to explore its properties.Word games are generally engaged as a source of entertainment, but have been found to serve an educational purpose as well...

 that requires simple mathematical operations, and vocabulary

Vocabulary

A person's vocabulary is the set of words within a language that are familiar to that person. A vocabulary usually develops with age, and serves as a useful and fundamental tool for communication and acquiring knowledge...

 skills to be solved. The solution is always a single word that contains four or more letters.

A WSP has a clue

Clue

Clue may refer to:* Cluedo , a crime fiction board game** Clue , based on the board game** Clue , based on the board game** Clue , based on the board game...

 and two or more hints, where the clue is a meaning for the solution (a single word) and each hint gives the sum of the numbers assigned to the first two, four, etc. letters of the solution^[1]. In an English WSP, the numbers assigned to the letters are as the same of their orders in English alphabet

English alphabet

The modern English alphabet is a Latin alphabet consisting of 26 letters and 2 ligatures – the same letters that are found in the Basic modern Latin alphabet:...

:

A, a = 1
B, b = 2
C, c = 3
D, d = 4
…
Z, z = 26

Example

A curved part of a path:

_ _ (7)

_ _ _ _ (25)

The first line of the puzzle

Puzzle

A puzzle is a problem or enigma that tests the ingenuity of the solver. In a basic puzzle, one is intended to put together pieces in a logical way in order to come up with the desired solution...

 presents a clue; in this puzzle, "A curved part of a path" is the puzzle’s clue. The other lines of the puzzle are its hints. This puzzle has two hints:

FIRST HINT
_ _ (7)

This hint indicates that the first two letters of the answer make a sum of 7. Hence, the first two letters can be:
A & F (or F & A), B & E, C & D or D & C

SECOND HINT
_ _ _ _ (25)

This hint indicates that the first four letters of the answer make a sum

SUM

SUM can refer to:* The State University of Management* Soccer United Marketing* Society for the Establishment of Useful Manufactures* StartUp-Manager* Software User’s Manual,as from DOD-STD-2 167A, and MIL-STD-498...

of 25. But based on the first hint, it is already known that the first two letters made a 7, therefore the third and fourth letters make a sum of 18. So they can be:
A& Q, B & P, C & O, D & N, E & M, … I & I

To solve the puzzle, the player should find which two pairs of letters obtained from these hints can make a word that means “A curved part of a path”.

A & F + A & Q – (NO)
A & F + B & P – (NO)
…
B & E + D & N (YES)
The solution for this example is "bend".