Divide ⅚ by ¾=(5/6)/(3/4)=(5/6)(4/3)=(4/6)(5/3)=10/9.
So ⅚=(10/9)×¾. 10/9=11/9. So to find ⅚ of a number, find ¾ of it then add to it one ninth of the result. For example, to find ⅚ of 120, we get 90 (¾ of 24) and one ninth of 90=10, and 90+10=100 which is ⅚ of 120.
⅗/¾=(3/5)(4/3)=⅘. To find ⅗ of a number, find ¾ of it then ⅘ of the result. For example, take 120 again, ¾ of it=90 and ⅘ of 90=72, which is ⅗ of 120.