习题21，几个简单的加减乘除函数，注意return的用法。

def add(a,b):
print(f"ADDING {a}+{b}")
return a+b

def subtract(a,b):
print(f"SUBTRACTING {a}-{b}")
return a-b

def multiply(a,b):
print(f"MULTIPLY {a}*{b}")
return a*b

def divide(a,b):
print(f"DIVIDE {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(f"Age: {age}, Height: {height}, Weight: {weight}, IQ: {iq}")

 

print("Here is a puzzle.")

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

print("That becomes:",what,"\n","Can you do it by hand?")