Simplifying the expression by first combining like terms:

2/3a + 1/2a = (2/3 + 1/2)a
= (4/6 + 3/6)a
= 7/6a

1/7b - 2b = (1/7 - 14/7)b
= (-13/7)b

-3/4c + 4c = (-3/4 + 16/4)c
= (13/4)c

Putting it all together:

7/6a - 13/7b + 13/4c