Answer:
9/10
Step-by-step explanation:
you find the lowest common denominator in this case is 10
then you take 1/2 and multiply it by 5 both the bottom and top and then you should get 5/10
next you do the same with 2/5 but this time to the get the denominator to 10 you multiply by 2 again multiply both bottom and top and you should get 4/10
now you just add 4/10 and 5/10 together and you get 9/10 or 0.9 as a decimal
