Please explaine how i would do this problem....

8 1/9 - 1 6/7 = ?????

before you substract, you need to find the common denominator...so the common denominator for 9 and 7 is 63. so you change both into the denominator to 63. there you have 8 7/63-1 54/63 which is 394/64 in improper fraction then you simplify it.