Ok in order to subtract this 2 fractions you have to find the smallest common factor for the bottom number in them both. The smallest common factor is the a number that can be used to identify the 2 bottom numbers(note that the number has to be bigger than both of the numbers, because you have to be able to multiply the bottom numbers with another one to get the common factor) Ok the number that fits both the 12 and 20 is the 60 this is the smallest number taht can be used to identify the 12 and 20, after you have your number you have to find the number that it is needed to multiply the bottom numbers to get 60.... For example, the first fraction is 5/12 what number can be multiplied by 12 to get 60?? well it will be 5( note that what you do to the bottom number you have to do to the top too) so if we multiply 12 times 5 we also have to multiply 5 times 5 this gives you the result of 25/60. Ok we have reached our number here so lets go with the second fraction, this one is 3/20. what number do we multiply by 20 to get 60?? well it will be 3 again multiply it by the bottom and top number to get 6/60 now that we have both denominators the same lets subtract 25/60-6/60( note that the bottom number always stays the same) the answer would be 1/60. we always have to check if we can simplify, in this case we can because there is number that can divide both numbers.... So your finla answer should be 4/15
Hope this helps
