I know how to this in one of two ways and I'm not sure if they're correct but anything to help.
5/6-2/5 would get you 1/3 because if you cross multiply and cross out factors that can go into each you cant pretty much get that answer. ( i think)
or
the common denominator would be 30 multiply 5 by 5 and 2 by 6. 25-12 is 13. How I was taught was find a number that both denominators can go into then multiply by that number. So 6*5= 30 so you would multiply 5 by 5 to get 25.
Hope I explained this well, I don't really think so.
