a, 128-[ 68+8 . ( 37-35 ) ² ]
= 128 - [ 68 + 8 . 2² ]
= 128 - [ 68 + 8 . 4 ]
= 128 - [ 68 + 32 ]
= 128 - 100
= 28
b, 107-{ 38+[7.3 ²-24:6+(9-7)³ ] } : 15
= 107 - { 38 + [ 7 . 9 - 4 + 2³ ] } : 15
= 107 - { 38 + [ 63 - 4 . 8 ] } : 15
= 107 - { 38 + [ 63 - 32 ] } : 15
= 107 - { 38 + 31 } : 15
= 107 - 69 : 15
= 107 - 4,6
= 102,4
c, 2020 + [38-(7-1)² - 2020^0 ]
= 2020 + [ 38 - 6² - 1 ]
= 2020 + [ 38 - 36 - 1 ]
= 2020 + [ 2 - 1 ]
= 2020 + 1
= 2021