The answer would be "-3/8 + -1/10."
Simplify means to reduce so in this case we aren't solving the question we are reducing it into simpler terms.

According to the rules of KCC (Keep Change Change) you would have to turn the subtraction sign into a addition sign and make the positive 1/10 into a negative.

The equation cannot be reduce no further therefore that would be your answer.
Hope this helps.