c=x-2y
y-2x=11
You asked:
Solve the system of equations:\[\begin{aligned}c &= x - 2 y\\y - 2 x &= 11\end{aligned}\]
MathBot Answer:
The system of equations has infinitely many solutions.
$$\begin{aligned}c &= - \frac{3 y}{2} - \frac{11}{2}\\x &= \frac{y}{2} - \frac{11}{2}\end{aligned}$$
\(y\) is a free variable.