Equivalent resistance between A and B 
Can someone point me in the direction so that these questions can be solved? A hint would be enough.
 A: The "most general" approach uses Kirchhoff's rules. You assume a little loop of current in each part of the circuit, and write down the voltage across each resistor as the product of (sum of) current and resistance. In the general case this gives you N simultaneous equations to solve (6 for the first, 5 for the second) - tedious, but doable.
However, when you look carefully at your diagrams you can see there is symmetry - in the first case, it is "left-right", in the second case, "top-bottom". This allows you to write a reduced set of equations with just three variables, which is much easier to solve.
In some special cases you can see further symmetries - for example you might spot a balanced Wheatstone bridge, so you can remove resistors that you know have no voltage across them, and simplify the circuit diagram further.
Once you have solved for all the currents, you can compute the current flowing out of A and into B - and you can compute the voltage from A to B. Those two things will then give you the equivalent resistance.
See if that gets you going.
