To add fractions with different denominators you must convert the denominators into the lowest common factor. Aka the multiple they all go into. You then times the numerator by what you timsed the denominator by to make sure they both have the same denominator.
Example:
2/5+4/10
They both go into 10.
4/10+4/10= 8/10. 2 became 4 because 5x2=10.
I hope this helped!
You could also simplify 8/10 into 4/5z
