Answer :
hello!
Let's combine like terms:-
[tex]\bigstar{\sf{-4k+15k-30=-78}[/tex]
Add the k's:-
[tex]\bigstar{\sf{11k-30=-78}[/tex]
Add 30 to both sides:-
[tex]\bigstar{\sf{11k=-78+30}[/tex]
[tex]\bigstar{\sf{11k=-48}[/tex]
Divide both sides by 11:-
[tex]\bigstar{\boxed{\sf{k=4.36}}[/tex]
note:-
Hope everything is clear; if you need any clarification/explanation, kindly let me know, and I will comment and/or edit my answer :)