Look up or assign value from another column

[Hilda_Python]

Hi. new coder here.
I have to find the oldest and newest housing block and find the price difference between them. I need to find the max/min and lookup or assign the corresponding house value from the 'house_value' column.
I can't get the price difference. it keeps coming up with a tuple error.

in advance, thnks. dammit, it's so easy but so hard.

import pandas as pd
import numpy as np
import math 

# read datafile 
df=pd.read_csv ("housing_dataset.csv")
df2=df[['housing_age','house_value']]

#find oldest house etc
oldest_house = np.max(df2)
newest_house = np.min(df2)
print ("The oldest house is : " , oldest_house)
print ("The newest house is : " , newest_house)

#find the house value
x = (oldest_house, 'house_value')
y = (newest_house, 'house_value')

print(x)
print(y)

diff = x - y
print(diff)

Output:
The oldest house is :  housing_age        52
house_value    500001
dtype: int64
The newest house is :  housing_age        1
house_value    14999
dtype: int64
(housing_age        52
house_value    500001
dtype: int64, 'house_value')
(housing_age        1
house_value    14999
dtype: int64, 'house_value')

Error:
TypeError                                 Traceback (most recent call last)
<ipython-input-292-83b8727a34d2> in <module>
     19 print(y)
     20 
---> 21 diff = x - y
     22 print(diff)

TypeError: unsupported operand type(s) for -: 'tuple' and 'tuple'