Combine the like terms. Don’t forget when you add fractions you must have the same denominator
(3/4)a - (1/2)a + (1/2)a = (3/4)a
- because the (1/2)a cancels out leading back to the original number
(2/3)-(1/3) = 1/3
To put it all together your simplified expression would be (3/4)a + (1/3)