1) [(a-2)/(a+2) - (a+2)/(a-2)] : 12a²/(4-a²) = [(a-2)² - (a+2)²] / (a² -4) : 12a²/(4-a²)=
= (a² - 4a + 4 - a² - 4a - 4) / (a²-4) : 12a²/(4-a²) = (-8a)/(a²-4) : 12a²/(4-a2) =
= 2/3a
2) (8x/(x-2) + 2x) : (3x+6)/(6x-12) = (8x + 2x² - 4x)/(x-2) : [ 18(x+2)/(x-2)] =
= 2x(x+2)/(x-2) : [18(x+2)/(x-2)] = x/9
3) 3a/(a-4) - (a+2)/(2a-8) * 96/(a² +2a) = 3a/(a-4) - [(a+2)/2(a-4) * 96/a(a+2)] =
= 3a/(a-4) - 48/ a(a-4) = (3a² - 48)/ a(a-4) = [3(a-4)(a+4)]/a(a-4) =
= 3(a+4)/a