Rearrange the terms on the left side:
2x² - 5 = -6x
Add 6x to both sides:
2x² + 6x - 5 = 0
This is not easily factored; so I would suggest that you use the quadratic formula:
x = [ -b ± √( b² - 4ac ) ] / ( 2a )
where, for this problem, a = 2, b = 6, and c = -5.