Use Kirchhoff's laws to write down 3 loop equations for voltage drops, and 3 node equations for currents.
I need to find the equivalent resistance and the current at I
I'm not sure where to start, I need to use Thevenins theorem? And it's a Wheatstone bridge?
If I take out the diagonal 3ohm resister which represents the load (I think this is the first step?) I'm not sure what to do next?
Here's a way to cut down on the work a bit. Use the rules for combining resistors in series or in parallel to simplify the circuit. For a start, the two 3Ω resistors that I have labelled in blue in the attachment are equivalent to a single 6Ω resistor. That can be combined with the green 3Ω resistor, using the rule for combining resistors in parallel, to form a single resistor. That single resistor is in series with the yellow 2Ω resistor, so again you can reduce them to a single resistor.
You then have a simplified circuit which has two links going from c to d in the diagram: there is a current through the 1Ω resistor , and a current I_3 through the equivalent resistor that you have formed from the blue-green-yellow resistors. Now you start to use Kirchoff's laws, but with only three variables instead of five.
Alex - I'm glad you're making a game attempt at this, but your equations are somewhat off.
I1 != I2 + I3 + I4 + I5 ( where != means does not equal )
Is it clear that segments DA, AB and BC all have I1 flowing in them? If not, think of a bus leaving node D and going counterclockwise. There is no place for the current to change until it hits node C. That's why the current is the same in all those segments. Once you hit node C, you see that all the current going into node C must come out of there. That gives:
I1 = I2 + I3.
Likewise the node E equation is:
I3 = I4 + I5
If you ask what the node F equation is, it is:
I5 = I5 (I5 going in, I5 going out).
Can you write down what the node D equation is?
Your loop equations ( for voltage ) are better. However you need to correct what current is running in R2 and R4. Also, you must make sure that the sign of the voltage drop is consistent (is a positive drop with or against current?).
You can also use OpAlg's suggestion to simplify the circuit somewhat - combine resistors in series (R4 and R7), then in parallel (R5 and the effective (R4/R7)), etc. Still, you do need to get familiar with writing down general Kirchhoff equations for a general circuit.
It looks like you've gotten the hang of it. Yes, you can continue to simplify the circuit in the way you described. However, as OpAlg points out, you've just simplified your problem out of existence! So back up one step and I think you're there. Good work!