\begin{align}
ΣF_x=0
=&\cssId{Step1}{F_{Ax} + F_{Bx} + F_{Cx}=0}\\[3px]
&\cssId{Step2}{F_A + F_B * cos(α) + F_{Cx}=0}\\[3px]
&\cssId{Step3}{F_{Cx}= -F_A -F_B * cos(α)}\\[3px]
\end{align}

- In the first step we make the summation of forces in the x-axis
- In the second step we express F
_{Bx}as F_{B}multiplying the cosine of the angle (doing trigonometry) - In the third step we isolate F
_{Cx}to one side of the equation and everything else to the other side so that you can solve the equation