Given all the weights and the total capacity of the elevator, we have the following expression:
[tex]11.6+45.8+62.3+x\leq180[/tex]where 'x' denotes the weight of the third case.
Solving for x, we get the following:
[tex]\begin{gathered} 11.6+45.8+62.3+x\leq180 \\ \Rightarrow119.7+x\leq180 \\ \Rightarrow x\leq180-119.7=60.3 \\ x\leq60.3 \end{gathered}[/tex]therefore, the third case must weigh 60.3 kg or less.