Solution to 11.

11. If that pen doesn't leak or the ink is not permanent, then your shirt is safe.

The simple statements are

P = The pen leaks.

I = The ink is permanent.

S = Your shirt is safe.

Substituting we get

If not-P or not-I, then S

Grouping in the obvious way we get:

If (not-P or not-I), then (S)

Which yields: