a) `37. 42 + 58. 37 - (88. 21 + 12. 21)`
`= 37. (42 + 58) - [21. (88 + 12) ]`
`= 37 . 100 - [21. 100 ]`
`= 3700 - 2100`
`= 1600`
b) `2020^2021 : 2020^2020 - 2020`
`= 2020^(2021 - 2020) - 2020`
`= 2020 - 2020`
`= 0`
c) `4. 5^2 - 64 : 2^3`
`= 4 . 25 - 64 : 8`
`= 100 - 8`
`= 92`