Change a fraction with a negative numerator and a negative denominator to a positive fraction by eliminating both negative signs. For example, if you see a fraction such as -2/-3, simply rewrite it as 2/3.
Consider a fraction with one negative sign as a negative fraction. The negative sign can be to the left of the entire fraction or to the left of the denominator.
Add a negative fraction and a positive fraction with like denominators by subtracting the smaller numerator from the larger one and attaching the sign of the larger numerator. For example, -2/5 + 3/5 would equal 1/5. Another example would be the addition of -2/5 and 1/5, the sum of which would be -1/5.
Add two negative fractions with like denominators by adding the numerators and attaching a negative sign. For example, -3/11 plus -4/11 would equal -7/11.
Subtract negative fractions with like denominators by changing the sign of the second numerator and adding the two numerators together. For example, consider the problem
-5/9 - 2/9. Rewrite the problem as -5/9 + -2/9, which would equal -7/9.
Multiply the numerators times each other and the denominators times each other in a multiplication sentence involving fractions. If you multiply two negative fractions, the answer will be positive. If you have one negative and one positive, the answer will be negative. For instance, -1/3 times -6/7 equals 6/21. In contrast, 1/3 times -6/7 equals -6/21.
Divide negative fractions by reversing the numerator and denominator of the second fraction to create a reciprocal. Then multiply the fractions. Add a negative sign if only one fraction is negative. For example, consider the problem 3/5 / -2/3. Change this to 3/5 x -3/2. Multiply to get -9/10. If the original fractions had both been negative in this example, the answer would've been 9/10.