First, we need to find the values of sin(240°), tg(120°), and cos(540°).

sin(240°) = sin(240° - 180°) = sin(60°) = √3/2

tg(120°) = sin(120°) / cos(120°) = √3 / (-1/2) = -√3 * 2 = -2√3

cos(540°) = cos(540° - 360°) = cos(180°) = -1

Now, we substitute the values into the equation:

2sin240 + tg120 - cos540
= 2 * (√3/2) + (-2√3) - (-1)
= √3 - 2√3 + 1
= -√3 + 1

Therefore, the final answer is -√3 + 1.