Aturtle is 20 5/6 inches below the surface of a pond. it dives to a depth of 32 1/4 inches. what is the change in the turtle’s position?

The turtle is initially 20 5/6 inches below the surface. 
After which he dives to a depth of 32 1/4 inches
then the initial position below - 20 5/6 inch
final position - 32 1/4 inch
the difference in the positions can be calculated taking the difference between initial and final position 
this can be done with a simple subtraction of fractions 
difference = 
when subtracting mixed fractions the whole numbers are first subtracted
  =  
  = 
 we can now bring the denominators to a common denominator which is 12
then in the first fraction 1/4, denominator is 4 , to bring it to 12 we can multiply the whole fraction by 3

next fraction 5/6 , denominator is 6, to bring it  to 12 we multiply whole fraction by 2

now since  3/12 is smaller than 10/12 so we borrow a whole number from 12 outside the brackets, then 
then 
 = (12 - 1) ()
  = 11 
therefore change in turtles position is 11 5/12 inches

The answer is c. 7 (i think) i’m almost sure though