A: Speed is Independent as it can be anything with no restrictions. Gas mileage is dependent as it relies on the value of speed for its value to be decided.
B: The first letter of speed is "S" so it can represent the variable. The first letter of mileage is "M" so the variable can be represented by that letter. It really can be any letter.
C: no context
D: no context
39, it is like the fibonacci sequence you take the 2 previous numbers and add them together to get the next number.
