−9.8+(−5.9)+u=−12.4
\({\color{red}-9.8+(-5.9)+u = -12.4}\) { - [- 9,8 + (-5.9) ]
\(u = -12.4 +9.8 -(-5.9)\)
\(u = -12.4 +9.8 +5.9\)
\({\color{blue}u=3.3}\) !
!
