The steps for subtracting fractions is well illustrated in the fraction calculator at the link below. That page has a more detailed discussion of common denominators, mixed fractions and other topics that may help understand the steps necessary to subtract fractions.
Skip counting is counting at intervals of whichever number you choose. For example, if I was to skip count by 7 I would count, 7, 14, 21… and so on. Using this method you can do single digit multiplication with ease. Say the teacher asks you to multiply 4 x 7 = __. You simply skip count 7’s, 4 times, 7, 14, 21, 28. The answer to 4 x 7 = 28.