1.

((1,2ав²)² + 0,7а*0,8ав⁴) / (2 1/3 а*9в - 1,9ав*10) =

= ((1,2ав²)² + 0,7а*0,8ав⁴) / (2 1/3 а*9в - 1,9ав*10) =

= (1,44а²в⁴ + 0,56а²в⁴) / (21ав - 19ав) =

= 2а²в⁴ / 2ав = ав³,

2.

2х * (-1/8ху)³ * (-2,5у²z) * (1/9xz²)² =

= 2х * (-1/512 х³у³) * (-2,5у²z) * 1/81 x²z⁴ =

= 5/41472 x⁶y⁵z⁵.

при  x = 3,  y = 2,  z = -1:

5/41472 * 3⁶ * 2⁵ * (-1)⁵ = 5/41472 * 729 * 32 * (-1) = -45/16 = -2 13/16