1. Tính :
a) \(32 + \left[ {6.\left( {11 + 1 - 4} \right)} \right]:8 + 12\);
b) \(168 - \left\{ {5.\left[ {143 - {{\left( {15 - 12} \right)}^2}} \right] + 10} \right\}:10.\)
2. Tìm số tự nhiên x, biết :
a) \(521 - \left( {145 - x} \right) = 381\);
b) \(\left( {6x - 39} \right):3 = 201\).
\(\eqalign{ & 1.\cr&a)\;32 + \left[ {6.\left( {11 + 1 - 4} \right)} \right]:8 + 12 \cr & = 32 + {\rm{[}}6.8]:8 + 12 \cr & = 32 + 48:8 + 12 \cr & = 32 + 6 + 12 \cr & = 50 \cr & b)\;168 - \left\{ {5.\left[ {143 - {{\left( {15 - 12} \right)}^2}} \right] + 10} \right\}:10 \cr & = 168 - {\rm{\{ }}5.{\rm{[}}143 - 9] + 10\} :10 \cr & = 168 - {\rm{\{ }}5.134 + 10\} :10 \cr & = 168 - 680:10 \cr & = 168 - 68 = 100 \cr & 2.\cr&a)\;521 - \left( {145 - x} \right) = 381 \cr & 145 - x = 521 - 381 \cr & 145 - x = 140 \cr & x = 145 - 140 \cr& x = 5 \cr & b)\;\left( {6x - 39} \right):3 = 201 \cr & 6x - 39 = 201.3 \cr & 6x - 39 = 603 \cr & 6x = 603 + 39 \cr & 6x = 642 \cr & x = 642:6 \cr& x = 107 \cr} \)