There are two c's. You must pay attention to capitalization, there's a lowercase c and an uppercase C which represent two different variables. Also, the W is capitalized which could make your answer incorrect if you don't use the same notation.
Solving for small c..
[tex] C = \frac{Wtc}{1,000} \\\\ 1,000C = Wtc \\\\\frac{1,000C}{Wt}= c [/tex]
So it's the answer shown in the picture, but it should be a capital W instead of a lowercase w.
