Instructions for operations with fractions

1. When one multiplies fractions, one simply multiplies "straight across:" numerator by numerator, denominator by denominator.
2. When one divides fractions, one may simply invert the "divided by" fraction, then multiply.
3. When adding and subtracting fractions, one must first find a common denominator (one divisible by all denominators being subtracted and/or added) and then add or subtract the numerators, keeping the common denominator as the final denominator. 
1. This works just as well whether or not the common denominator is the "lowest common denominator," but it is usually advantageous to use the lowest common denominator; particularly so if you are not using a calculator. 
2. If finding the "lowest" common denominator is less important to you, you may simply multiply the given denominators to find a common denominator. 
3. Each individual fraction in the problem must first be multiplied by 1: i.e., multiplied by the common denominator over the common denominator/
4. Always simplify (reduce) the answer when possible (for any operation).