Answer is 3/10
Step by step
To add or subtract fractions, the denominator (bottom number) must be the same.
Think of a pie that is cut into 5 pieces, you can’t take away 9 pieces.
9/10 - 3/5
10 would be the common denominator that both 10 and 5 are divisible
9/10 stays the same
3/5 we multiply the bottom x 2 to = 10
So we also multiply the top x 2
3/5 = 6/10
Now we subtract the numerators (top numbers)
9/10 - 6/10 = 3/10
3/10 is in its simplest form so it is your answer