## Precalculus (6th Edition) Blitzer

So, from equation (I) put the value of y in equation (II) and solve for x, \begin{align} & 21x-35=7\left( 3x-5 \right) \\ & 21x-35=21x-35 \end{align} $35=35$ (III) And according to equation (III), $35=35$ indicates that the system has infinitely many solutions.