Answer:
[tex]\huge\boxed{-3\overrightarrow{a}+5\overrightarrow{b}=\left<-21;\ 2\right>}[/tex]
Step-by-step explanation:
[tex]\overrightarrow{a}=\left<2;\ 6\right>\\\\\overrightarrow{b}=\left<-3;\ 4\right>\\\\-3\overrightarrow{a}+5\overrightarrow{b}=-3\left<2;\ 6\right>+5\left<-3;\ 4\right>=\left<-3\cdot2;\ -3\cdot6\right>+\left<5\cdot(-3);\ 5\cdot4\right>\\\\=\left<-6;\ -18\right>+\left<-15;\ 20\right>=\left<-6+(-15);\ -18+20\right>=\left<-21;\ 2\right>[/tex]