\[= - 18,31 - 6,27 - 8,44 + 31,67 =\]
\[= 31,67 - (18,31 + 6,27 + 8,44) =\]
\[= 31,67 - 33,02 =\]
\[= - (33,02 - 31,67) = - 1,35\]