Answer :

9/10-2/5 9/10-4/10 5/10 1/2
9/10-2/5

You first make the bottom number the same, so make them both 10.

9/10 is already n/10
2/5 is times by 2 to get n/10
2/5=4/10
Now you just do 9/10-4/10=5/10
Simplify 5/10 by dividing both sides by 5 gives 1/2 or 0.5 or a half