Question 77196
The first problem occured when you tried to square (k+8).  The answer would not be K^2 and 64.  The square that, you need to multiply like this:

(k+8)(k+8)  which gives:  k^2+16k+64.

You then have:

50+7k = k^2+16k=64

move the 50 and 7k to the other side:

k^2+9k+14=0

then you factor this equation:

(k+7)(k+2)

setting each of these = to 0 to solve for k you get:

k+7=0  and k+2=0

k= -7 or  -2 <----  answer

Hope this helps!!!