9/10.
To find this, first find a common denominator between the two fractions. For this problem, the common denominator will be 10. With this information, you can leave 3/10 as it is, but you'll need to change 3/5. In order to make it so this has the common denominator of 10, you need to multiply the numerator (3) by two before changing the denominator.
After this is done, proceed to add. It cannot be simplified any further, thus giving you the final answer of 9/10.
Hope this helps!