So in lesson 11 we learned an A major scale had 3 sharps (F#, C#, G#).  In this lesson we will learn that an E major scale has 4 sharps (F#, C#, G#, D#).  We used the major scale formula:

W  W  H  W  W  W  H

We also learned that A majors relative minor was F#

E majors relative minor is C#

So both the key of E major and the key of C# have 4 sharps and those are:

F#, C#, G# and D#