Question 1130825
Go according to what the description literally says.


{{{system(L=K+13,J=7+6K)}}}
and just one more equation is necessary to know:

{{{J+K+L=180}}}



As described, you can write the angle-sum equation in terms of just one variable, K.
{{{(7+6K)+K+(K+13)=180}}}
Solve!