Final answer:
To add the fractions, convert both fractions to have a common denominator and then add the numerators.
Step-by-step explanation:
To add fractions, we need to find a common denominator. In this case, the least common denominator of 25 and 35 is 175.
Converting both fractions to have a denominator of 175:
-18/25 = -126/175
6/35 = 30/175
Now add the numerators:
-126/175 + 30/175 = -96/175
Therefore, the answer is (-96 / 175).