find a common denominator by using the multiplication by 1 law. anything divided by itself is 1 and anything multiplied by 1 is itself. so the first time 10 and 15 can meet is us at 30. 10 must be multiplied by 3 to get 30.
Using the laws stated earlier: (4/10) * 1 = 4/10, and 3/3 = 1, so substitute 3/3 for 1 in first equation (4/10) * (3/3) = 12/30.
Now same for other fraction: (2/15) * (2/2) = 4/30
Now subtract the 2 equivalent fractions and the answerr is: (12/30) - (4/30) = 8/30 or 4/15
