8.1

###Question 1
def mystery(x, y):
    result = (x + y) / (y - x)
    return result

print(mystery(2,3))



##Question 2

def main():
    a = 5
    b = 7
    print(mystery(a, b))

def mystery(x, y):
    z = x + y
    z = z / 2.0
    return z
main()



## Question 3

def main():
    a = 4
    print(mystery(a + 1))

def mystery(x):
    y = x * x
    return y
main()



##Question 4

def evenPage(p):
    if p % 2 == 0:
        return True
    else:
        return False

p = int(input('Please input a page number: '))

if evenPage(p) == True:
    print(p)
else:
    print("%60s%d" % (" ", p))



##Question 5



def count_spaces(userinput):
    spaces = 0

    for char in userinput:
        if char == " ":
            spaces = spaces + 1
    return spaces

def main():
    
    userInput=input('enter sentence: ')
    s = count_spaces(userInput)
    print(s)


main()


###Question 6

def mystery(n):
    if n <= 0 :
        return 0

    else:
        return n + mystery(n - 1)

def main():
    print(mystery(4))
main()



##question 7

def mystery(n) :
    if n <= 0 :
        return 0

    else:
        return mystery(n // 2) + 1
def main():
    print(mystery(20))
main()



##Question 9

def f(a) :
    if a < 0 :
        return -1

    n = a

    while n > 0:
        if n % 2 == 0: # n is even

            n = n // 2

        elif n == 1:
            return 1

        else:
            n = 3 * n + 1

        return 0




def main():
    t = f(-1)
    print(t)

    t = f(0)
    print(t)

    t = f(1)
    print(t)

    t = f(2)
    print(t)

    t = f(10)
    print(t)

    t = f(100)
    print(t)

main()