這是我自己學習的答案，會盡力寫的比較好。還望大家能夠提出我的不足和錯誤，謝謝！

文中例題：

def add(a, b):
    print "ADDING %d + %d" % (a, b)
    return a + b

def subtract(a, b):
    print "SUBTRACTING %d - %d" % (a, b)
    return a - b

def multiply(a, b):
    print "MULTIPLYING %d * %d" % (a, b)
    return a * b

def divide(a, b):
    print
 
 "DIVIDING %d / %d" % (a, b)
    return a / b


print "Let's do some math with just functions!"

age = add(30, 5)
height = subtract(78, 4)
weight = multiply(90, 2)
iq = divide(100, 2)

print "Age: %d, Height: %d, Weight: %d, IQ: %d" % (age, height, weight, iq)

# A puzzle for the extra cerdit, type it in anyway.
 

print "Here is a puzzle."

what = add(age, subtract(height,multiply(weight, divide(iq, 2))))

print "That becomes: ", what, "Can you do it by hand?"

執行結果：

習題答案：

1、這裡提個C語言中的左值右值。大概理解就是左值是一個地址，右值是一個數據。
2、
其實就是分解計算了原先what的運算：
原先what的運算：

what = add(age, subtract(height,multiply(weight, divide
 
(iq, 2))))

改為：

temp1 = divide(iq, 2)

temp2 = multiply(weight, temp1)

temp3 = subtract(height, temp2)

what = add(age, temp3)

4、

def add(a, b):
    print "ADDING %d + %d" % (a, b)
    return a + b

def subtract(a, b):
    print "SUBTRACTING %d - %d" % (a, b)
    return a - b

def multiply(a, b):
    print "MULTIPLYING %d * %d" % (a, b)
    return a * b

def divide(a, b):
    print "DIVIDING %d / %d" % (a, b)
    return a / b

age = 1
height = 1
weight = 4
iq = 4

what = 100

temp3 = subtract(what, age)
temp2 = add(temp3, height)
temp1 = divide(temp2, weight)
temp = multiply(temp1, iq)

print "answer is %d " % temp