In order to find 5a-3b, lets find 5a. This is given by
[tex]\begin{gathered} 5a=5(-2,1) \\ 5a=(-10,5) \end{gathered}[/tex]Similarly, -3b is given by
[tex]\begin{gathered} -3b=-3(5,4) \\ -3b=(-15,-12) \end{gathered}[/tex]Then, by substituting our results into the expression 5a-3b, we get
[tex]5a-3b=(-10,5)+(-15,-12)[/tex]This can can be done by adding entry by entry, that is
[tex]5a-3b=(-10-15,\text{ 5-12)}[/tex]Therefore, the answer is
[tex]5a-3b=(-25,-7)[/tex]