To solve this expression, we need to follow the order of operations (PEMDAS/BODMAS).

First, let's simplify the expression inside the parentheses:
3/5:(-3/2) = 3/5 * (-2/3) = -6/15 = -2/5

Now, let's add the fractions:
2/5 + (-2/5) + 1/2

To add fractions, we need a common denominator. The common denominator here is 10.

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

Now, we can add the fractions:
4/10 + (-4/10) + 5/10 = (4 - 4 + 5)/10 = 5/10 = 1/2

Therefore, 2/5 + 3/5:(-3/2) + 1/2 = 1/2.