Ideal Transformer Theory Question
First noting that we are talking about ideal transformers...

You must first find the value of the impedance reflected back to the primary from the secondary side, then you can find the total impedance on the primary side. From this you can calculate the primary current, given the source voltage.

If your not sure what happens on the primary side if the secondary is open or shorted, think about what would happen as the impedance on the secondary got really, really big or really, really small. This will tell you what would happen if the secondary was open (\$Z = \infty\$) or shorted (\$Z = 0\$).

To find the output voltage you must first find either \$I_1\$ or \$V_1\$, then you can use the turns ratio to find the current or voltage on the secondary side. From that point the usual circuit analysis techniques apply.