To simplify the expression, we first distribute the coefficients:

12(17а-5в+4) = 12 17а - 12 5в + 12 4 = 204а - 60в + 48
27(4а+7в+1) = 27 4а + 27 7в + 27 1 = 108а + 189в + 27

Now, we combine the like terms:

204а - 60в + 48 - 108а - 189в - 27
= (204а - 108а) + (-60в - 189в) + (48 - 27)
= 96а - 249в + 21

Therefore, the simplified expression is 96а - 249в + 21.