Please help solve! I tried but I’m messing this up, would really appreciate it!

Answer:
K = [tex]\frac{4r}{n} -a[/tex] n [tex]\neq 0[/tex]
Step-by-step explanation:
We have our equation [tex]r = \frac{n}{4} (a+K)[/tex] and are looking for K
First we have to switch sides :
[tex]\frac{n}{4} (a+K) = r[/tex]
Since we have a denominator of 4, we multiply both sides by 4 :
[tex]n (a+K) = 4r[/tex]
We then divide both sides by n :
[tex]a+K = \frac{4r}{n} ; n\neq 0[/tex]
Subtract a from both sides :
[tex]K = \frac{4r}{n} -a; n\neq 0[/tex]
^^^