This generates a game where there is an algebraic expression whose operations are hidden.

number_game.py

import random

def generate_game(largest_number, length, difficulty):
    """Produce an example of the number game.
    - largest_number is the largest possible number that can appear
    - length is how many numbers will appear in the problem
    - difficulty = 0,1,2. 0 has just addition/subtraction, 1 introduces multiplication, 2 has +,-,*,/
    """
    # Set difficulty
    operations = ["add", "subtract"]
    if difficulty > 0:
        operations.append('multiply')
    if difficulty > 1:
        operations.append('divide')
    
    # Add numbers and operations
    game = [random.randint(0,largest_number)]
    for i in range(length-1):
        game.append(random.choice(operations))
        game.append(random.randint(0,largest_number))

    # Find solution
    copy_game = copy(game)
    while 'multiply' in copy_game:
        i = copy_game.index('multiply')
        copy_game = copy_game[:i-1] + [(copy_game[i-1]*copy_game[i+1])] + copy_game[i+2:]
    while 'divide' in copy_game:
        i = copy_game.index('divide')
        copy_game = copy_game[:i-1] + [(copy_game[i-1]/copy_game[i+1])] + copy_game[i+2:]
    while 'subtract' in copy_game:
        i = copy_game.index('subtract')
        copy_game = copy_game[:i-1] + [(copy_game[i-1]-copy_game[i+1])] + copy_game[i+2:]
    solution = sum(copy_game[::2])
    
    # Make hidden game
    hidden_game = ""
    for i in range(len(game)):
        if i % 2 == 0:
            hidden_game += str(game[i])
        else:
            hidden_game += " _ "
    hidden_game += " = " + str(solution)
    print hidden_game
    
    x = raw_input("Click to see a solution.")
    print game
    return None

s = int(raw_input("What's the largest number you want to appear? (Enter a whole number larger than 0)"))
l = int(raw_input("How many numbers do you want to appear? (Enter 1,2, ..., 10)"))
d = int(raw_input("What difficulty do you want? 0 = + and - only, 1 contains multiplication, 2 contains all operations."))
for i in range(int(raw_input("How many games do you want to play? (Enter 1,2, ..., 10)"))):
    generate_game(s, l, d)
print "Thank you for playing!"