a)
24 : ( - 4 ) - [ 68 + ( - 4 )³ ] - 20 = - 30
= - 6 - ( 68 - 64 ) - 20 =
= - 6 - 4 - 20 =
= - 30
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b)
16 × ( - 2 )³ - 44 - 78 - 30 = - 124
= 16 × ( - 8 ) - ( 44 - 78 ) - 30 =
= - 128 - ( - 34 ) - 30 =
= - 128 + 34 - 30 =
= - 124