\(10-0,25\cdot0,125\cdot32\\ =10-\left(0,125\cdot32\right).0,25\\ =10-4.0,25\\ =10-1\\ =9\)

\(5^{20}-5^{29}=5^{20-29}=5^{-9}\)

\(b.385,89-x=1,34\cdot2,3\\ =>385,89-x=3,082\\ =>x=385,89-3,082\\ =>x=382,808\)

\(2023^2-2023\cdot2022\\ =2023.2023-2023.2022\\ =2023.\left(2023-2022\right)\\\\ =2023.1\\ =2023\)

\(x:0,5+x\cdot8=43,2\\ =>x:\dfrac{1}{2}+x.8=43,2\\ =>x\cdot2+x.8=43.2\\ =>x.\left(2+8\right)=43,2\\ =>x.10=43,2\\ =>x=43,2:10\\ =>x=4,32\\ \)

\(x+x\cdot0,25=4,8\\ =>x.\left(1+0,25\right)=4,8\\ =>x.1,25=4,8\\ =>x=4,8:1,25\\ =>x=3,84\)

123 . 456 + 456 . 321 - 256 . 444

= 456 . (123+321) - 256 . 444`

= 456 . 444 - 256 . 444

= 444 . (456-256)

= 444 . 200 

 = 88800

`87 xx 2 xx 5`

`= 87 xx ( 2 xx 5)`

`= 87 xx 10`

`= 870`