The answer will be 0.932057
Try this explanation/solution:
a) the system which describes this situation is:

b) the solution of the system made up:

The answer is 11.21, dividing 6.391 by 0.57 will give you 11.2122807018.
Rounding to 11.21 because the thousandths place is less then 5 so the hundredths place stays the same.
(numeral)~(decimal)~(tenths)(hundredths)(thousandths)