Tracy had an initial amount of $200, but as she already spent $134, now she has the difference between those numbers.
Now she has $66. Each video game costs $20, to find the number of video games she can buy with $66, divide 66 by 20.
The result is 3.3 but, as she can't buy 3.3 video games, we say that the maximum number of video games she can buy is 3.