First of all, don't let "b" confuse you. Know that b = 5/6k = -10, so all you really have to solve for this problem is [tex]\frac{5}{6}k = -10[/tex].
Before anything else, you have to isolate k. Do this my multiplying both sides by the reciprocal of 5/6.
[tex]\frac{6}{5} * \frac{5}{6}k = -10 * \frac{6}{5}[/tex]
The 6/5 and 5/6 cancel each other out, so we are left with [tex]k = -10 * \frac{6}{5}[/tex]
--> [tex]k = \frac{-10 * 60}{5}[/tex]
---> [tex]\frac{-60}{5} = -12[/tex]
So k = -12.
Hope this helped. Good luck.
