from a rope 23m long, two piece of long ths 12/7m and 7/4 are cut off . what is the length of the remains rope?

Answer 1

12/7 + 7/4 = 48/28 + 49/28 = 97/28 = 3 13/28
so what's left is 23 - 3 13/28 = 19 15/28