Answer:
1/10
Explanation:
There are three simple fractions in this problem: 3/5, -1/4 and 7/10. Rules of order require that the division (-1/4) divided by 7/10 be carried out first; the correct product is -10/28, or -5/14. Then we have 3/5 + (-5/14).
Here the LCD is 70. Then 3/5 + (-5/14) becomes 42/70 - 35/70, which simplifies to 1/10.