A linear system may have a unique solution, no solution, or infinitely many solutions. Indicate the type of the system for the following examples by U , N , or I , respectively.
1. $\begin{array}{rrcl}2x+3y&=&5\\ 2x+3y &=& 6\\ \end{array}$
2. $\begin{array}{rrcl}2x+3y&=&5\\ 4x+6y &=& 10\\ \end{array}$
3. $\begin{array}{rrcl}2x+3y&=&5\\ 2x+4y &=& 6\\ \end{array}$

Hint: If you can't tell the nature of the system by inspection, then try to solve the system and see what happens.