To solve this expression, we need to first find a common denominator for the fractions.

The common denominator for 2, 10, 5, and 20 is 20.

Now, convert each fraction to have a denominator of 20:

-1/2 = -10/20
-7/10 = -14/20
-3/5 = -12/20
11/20 (already in terms of 20)

Now, substitute these values back into the expression:

(-10/20) + (-14/20) - (-12/20) - (11/20)

Now, simplify:

(-10/20) + (-14/20) + (12/20) - (11/20)
= (-10 - 14 + 12 - 11) / 20
= (-23) / 20

Therefore, (-1/2) + (-7/10) - (-3/5) - (+11/20) equals -23/20.