Starting with a).
For the first unit: 0 * x1 + 1 * x2 + 1 > 0 (0, because the threshold is 0) which is the same as x2+1 > 0.
For the second unit: x1 * 1 + x2 * 0 + 1 > 0 (0, because the threshold is 0) which is the same as x1 + 1 > 0.
For the third unit: x1 * 1 + x2 * 1 + 1 > -1 (-1, because the threshold is -1. I might have misunderstood this since the assignment states "Circles indicate threshold units with threshold at zero...") which is the same as x1 + x2 > -2.
I then draw those lines. Is it correct so far? I can't however figure out how to solve b) How do I take the bias on the output node into account?
This is the given solution (but I don't understand how they got it):