` a) 463 - [ 44 - 3 xx ( 2^3 xx 4 - 5^5 : 5^4)] `

` = 463 - [ 44 + 3 xx ( 8 xx 4 - 5^2 )] `

` = 463 - [ 44 + 3 xx ( 32 - 25)] `

` = 463 - ( 44 + 3 xx 7 ) `

` = 463 - ( 44 + 21 ) `

` = 463 - 65 `

` = 398 `

` b) 2^2 xx 5 + 1515 : 15 `

` = 4 xx 5 + 101 `

` = 20 +101 `

` = 121 `

` c) 2020 - [45 - ( 6 - 1 )^2] + 1992^0 `

` = 2020 - ( 45 - 5^2 ) + 1 `

` = 2021 - ( 45 - 25 ) `

` = 2021 - 20 `

` = 2001 `

` d) 10^10 : ( 2 xx 4 xx 5 xx 25 xx 10^5 ) `

` = 10^10 : ( 10 xx 100 xx 10^5 ) `

` = 10^10 : ( 10^1 xx 10^2 xx 10^5 ) `

` = 10^10 : 10^8 `

` = 10^(10-8) `

` = 10^2 `

` = 100 ` 

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