I have a 1993 honda 300 ex that i got in a trade.Well it has a oil leak.it is coming from the nut on the right back side of the motor.It is the nut the goes on the bolt that goes trough the back of the motor to attach the motor to the frame.How can oil be leaking from this.And how can i stop it or fix it.

 

There is no way oil is coming out of the Rear engine mount, as there is NO oil in that section of the case.. The case is sealed by a gasket there and its rather think.

Now IF for some reason you do have oil coming fram that AREA of the engine case. its coming from the gasket in between the left and right case.
Which will require the case be split and new gasket installed. $$$

You shure you didnt blow your rear shock and its dripping down onto the case?

Is your crank case breater T fitting still together? You maybe blowing out oil from the Breather tube. The tube might have pulled loose from the T fitting or just have a hole in it.

Clean the bike Extremly well. Fill it with oil. go ride it for a few mins and look to see where the oil is coming from.
I know you said where its leaking. But it could be coming from somewhere else and be wind blown to that location.