There are a few ways to answer this question. . .
One way is to realize that 9/8 hours is 1/8 more than 1 hour, so the plane will fly 570 miles plus 1/8 of 570 miles.
Another way is to set up a proportion . . . 570 miles is to one hour as X miles is to 9/8 hours:
570/1 = X / (9/8)
Now cross multiply--> 570 (9/8) = X
X = 641.25 miles