Many students at beginner university level math courses do the same kind of mistakes, albeit with larger numbers: 10/13 + 7/21 = 17/34. Decimals are much easier

Many students at beginner university level math courses do the same kind of mistakes, albeit with larger numbers: 10/13 + 7/21 = 17/34. Decimals are much easier to deal with imo, but mathematicians does not like them because they are inexact.