Chapter 7 - Algebra: Graphs, Functions, and Linear Systems - 7.3 Systems of Linear Equations in Two Variables - Exercise Set 7.3 - Page 445: 37

No solution and the solution set is\[\phi \].

Substitute\[x=9-2y\]in the equation\[x+2y=13\] to get: \[\begin{align} & 9-2y+2y=13 \\ & 9\ne 13 \end{align}\] Since\[9\ne 13\], it implies the system of the equation does not have a solution. Therefore, the solution set is\[\phi \].