1a/ 4.5^2 - 32 : 2^4
      = 100 - 512
      = -412
b/ 2^4 . 5 -[ 131 - ( 13 - 4) ^2]
  = 16 . 5-  ( 131 - 81)
= 80 - 50
= 30
c/ 160 - ( 2^3 . 5^2 - 6 . 25 )
= 160 - 50
= 110
d/ 100:{ 250 : [ 450 - ( 4 . 5^3 - 2^2 . 5^2 )]}
 = 100:[250 :( 450 - 400)
= 100 : ( 250 : 50 )
= 100: 5
= 20