To find tg X, first let's simplify the equation by dividing both sides by 2:

(sin x - cos x) / (2cos x + sin x) = 3 / 2

Now, we can use the trigonometric identity tan x = sin x / cos x to replace sin x and cos x:

(tan x - 1) / (2 + tan x) = 3 / 2

Now, cross multiply to get rid of the fraction:

2(tan x - 1) = 3(2 + tan x)
2tan x - 2 = 6 + 3tan x
2tan x - 3tan x = 6 + 2
-tan x = 8
tan x = -8

Therefore, tg X is -8.