You find the common denominator of each fraction. Since 10 and 6 both go into 30, that will be your new denominator for both of them. 10 x 3 = 30, and 6 x 5 = 30. Because you changed the denominator, you have to multiply the top number with the same number you did on the bottom. 7 x 3 = 21, and 1 x 5 = 5. You now have the fractions 21/30 and 5/30, then subtract resulting in 16/30. You can simplify it by dividing each number by 2 resulting in 8/15.
