a) -2/5 + 3/5 - 1/2

To add or subtract fractions, we need to have a common denominator. In this case, the common denominator is 10.

-2/5 + 3/5 - 1/2 = (-2/5)(2/2) + (3/5)(2/2) - (1/2)(5/5)
= -4/10 + 6/10 - 5/10
= ( -4 + 6 - 5 ) / 10
= -3/10

b) -4/3 - 2/7 + 4/3

Again, we need to find a common denominator, which is 21.

-4/3 - 2/7 + 4/3 = (-4/3)(7/7) - (2/7)(3/3) + (4/3)(7/7)
= -28/21 - 6/21 + 28/21
= (-28 - 6 + 28) / 21
= -6/21
= -2/7

c) 1/2 + (-4/5) - 3/10

We can add or subtract fractions directly since the denominators are already the same.

1/2 + (-4/5) - 3/10 = 1/2 - 4/5 - 3/10
= (1/2)(5/5) - (4/5)(2/2) - (3/10)(1/1)
= 5/10 - 8/10 - 3/10
= (5 - 8 - 3) / 10
= -6/10
= -3/5