Answer:
33,920 acres of forest were burned.
Step-by-step explanation:
In this case, since you know that a square mile is equal to 640 acres, you can use a rule of three to find the acres that are equivalent to 53 square miles:
  1 square mile   →   640 acres
53 square miles   →     x
x=(53*640)/1
x=33,920 acres
According to this, the answer is that 33,920 acres of forest were burned.