How to Understand adding and subtracting fractions

The video creator attempts to teach us how to add and subtract fraction. He goes very slowly and assumes that the viewer only has a very basic knowledge of math. He starts with a division of a pie. If we were to divide a pie into four pieces, you would get four pieces of a pie. If I ate one, there would only be three fourths of the pie left. He uses this basis in order to explain this mathematically.