Question: Why is fsolve unable to solve this simple linear system?

I'm doing a simple system of equations problem and for some reason fsolve doesn't give any answer. I know the system has a unique solution, it's actually pretty trivial to solve. This is what I have written:

sys = {1800*40+15*(300*30)-30*Biy = 0, -1800+Biy+Ciy-300*30 = 0};
      sys = {207000 - 30 Biy = 0, -10800 + Biy + Ciy = 0}
                       fsolve(sys, {Biy})

If I rewrite to manually solve one by one, like this:

fsolve(1800*40+15*(300*30)-30*Biy = 0);
                             6900.
fsolve((-1800)+6900+Ciy-300*30 = 0);
                             3900.

So obviously it can be solved. I want to know why it doesn't solve when put in the first way. By the way I know this is a really simple system, and obviously there is a way to work around this problem and get an answer. I'm asking because I want to understand better how solve works, and so I can avoid more difficult issues later.