This is the fourth question on page 5 of the first volume of second grade mathematics.
Solution: 63-36=27 =9*(6-3)
54-45=9 =9*(5-4)
64-46= 18 =9*(6-4)
After the position of any two-digit number is reversed, the difference with the original number is equal to 9 times the difference between the original ten-digit number and the single-digit number.