We have the next information
[tex]\begin{gathered} X=1200\rightarrow P(X)=0.2 \\ X=300\rightarrow P(X)=0.5 \\ X=-700\rightarrow P(X)=0.3 \end{gathered}[/tex]So, the the expected change is
[tex]\begin{gathered} 1200(0.2)+300(0.5)-700(0.3) \\ =240+150-210=180 \end{gathered}[/tex]Finally, the expected change in the number of electronics jobs in that city in the year is 180