In this assignment I want to use a simplified data to create a simple linear reg

In this assignment I want to use a simplified data to create a simple linear regression model. This link is where the data can be found https://www.kaggle.com/harlfoxem/housesalesprediction/download
My code snippets are attached as screenshots.
I’ve split the data to train and test datasets. Can you check if 2a) In [85] is correct? How can I use best_guess_predictor as a single predictor and build a simple linear regression model? I need the most help with problem 3b, but I would like my previous answers checked for inaccuracies.