b)812-4 x [6 x (61-3600:12:30)]:9
= 812 - 4 x [ 6 x ( 61 - 300: 30 )]: 9
= 812 - 4 x [ 6 x ( 61 - 10 )] :9
=812 - 4 x ( 6 x 51 ) :9
= 812 - 4 x 306 :9
= 812 - 1224 : 9
= 812 - 136
= 676
d) 2007 + 18 : [ 2 + (16 -4) : 3 ]
= 2007 + 18 :( 2 +12 :3)
= 2007 + 18 : ( 2 + 4)
= 2007 + 18 : 6
= 2007 + 3
= 2010
a este incomplet