repl.it
Python3

A program to answer a difficult elementary school math assignment.

main.py
words
# How many answers to find for each
COUNT=30

# These are the letters a-z
from string import ascii_lowercase as letters

# Assign values to each letter as given in the assingment
# stored as a dictionary with a: -13 and so on.
v = dict(zip(letters, range(-13, 13)))

# To store tuples of the calculated values
calculations = []

# "words" is a word list with one English word per line
with open('words', 'r') as words:
    for word in words:
        # Each line has a '\n' newline at the end, so strip it
        word = word.strip()
        # Ignore words that have capital letters or other characters
        if not set(word).issubset(set(letters)):
            continue
        # Enumerate the assigned values for letters in the word
        values = list((v.get(l, 0) for l in word))
        # String together a calculation (like +5-2+3...)
        calculation = ''.join(('%+d' % v for v in values))
        # Add a tuple of the word, the "show your work", and the total
        calculations.append((word, calculation, sum(values)))

# Sort the calculations by word length
calculations = sorted(calculations, key=lambda a: len(a[0]))

print('Find a word that has a value of 18.')
# Let's grab the longest five and the shortest 10
eighteens = list((c for c in calculations if c[2] == 18))
for answer in eighteens[:COUNT] + eighteens[-COUNT:]:
    print('%s: %s=%d' % answer)

print('Find a word that has a value of -16.')
# Let's grab the longest five and the shortest 10
minussixteens = list((c for c in calculations if c[2] == -16))
for answer in minussixteens[:COUNT] + minussixteens[-COUNT:]:
    print('%s: %s=%d' % answer)

# The next two questions are about values of 5
fives = list((c for c in calculations if len(c[0]) == 5))

# Sort from highest value to lowest
fives = sorted(fives, key=lambda a: - a[2])

print('Find the highest value 5 letter word you can.')
for answer in fives[:COUNT]:
    print('%s: %s=%d' % answer)

print('Find the lowest value 5 letter word you can.')
for answer in fives[-COUNT:]:
    print('%s: %s=%d' % answer)
Python 3.6.1 (default, Dec 2015, 13:05:11) [GCC 4.8.2] on linux