To subtract fractions, the denominators must be the same.

1/2 - 1/7

To find a common denominator between 2 and 7, we can multiply them together: 2 x 7 = 14.

Now we need to rewrite the fractions with a common denominator:

(1/2)(7/7) - (1/7)(2/2)
7/14 - 2/14

Now subtract the numerators:

7/14 - 2/14 = 5/14

So, 1/2 - 1/7 = 5/14

3/5 - 4/15

To find a common denominator between 5 and 15, we can multiply them together: 5 x 15 = 75.

Now we need to rewrite the fractions with a common denominator:

(3/5)(15/15) - (4/15)(5/5)
45/75 - 20/75

Now subtract the numerators:

45/75 - 20/75 = 25/75 = 1/3

So, 3/5 - 4/15 = 1/3