Ответ:

1) -a

2) -b

3) 1,8x

4) -a

Пошаговое объяснение:

1) -(3/10)*a*10/3 = -(3/10*10/3)*a = -1a = -a

2) 12/5*b*(-5/12) = -(12/5*5/12)*b = -1b = -b

3) (-18/25)*x*(-2,5) = 18/25*x*2,5 = (18/25*5/2)*x = 9/5x = 1,8x

4) 4,5*(-2/3)^3*a = 4,5*(-8/27)*a = -(9/2*8/27)*a = -1a = -a (3/3 = 1)