In a cyclic quadrilateral ( a quadrilateral that is inscribed in a circle),
opposite angles add up to 180 degrees. So you can form an equation and solve for x, and thus angle E.
Therefore:
(-2 + 6x) + (7x - 13) = 180
13x - 15 = 180
13x = 195
x = 15
So angle E = 5x
= 5 (15)
= 75 degrees
