ANSWER is 2/5
First you have to make the denominators of 1/2 and 4/5 the same.
You multiply 2 and 5 can both make 10. So you multiply the 2 times 5 to get 10. Whatever you do to the top you have to do to the bottom so 1/2 becomes 5/10
Then do the same to 4/5 and it becomes 8/10.
Now you just subtract 8/10 from 5/10 and you get 4/10
Lastly simplify and you have 2/5
Hope this helps