Determine whether the following systems have no solution, an infinite number of solutions or a unique solution. \text { 1. }\left\{\begin{array}{rrr} 25 x+15 y & =15 \\ -15 x-9 y

& =-9 \\ -30 x-18 y & =-18 \end{array}\right. \text { 2. }\left\{\begin{array}{rrr} -x+ & 3 y=7 \\ -4 x+ & 3 y=6 \\ -19 x+21 y & =46 \end{array}\right. \text { 3. }\left\{\begin{array}{rrrr} -x & + & 3 y & =7 \\ -4 x & + & 3 y & =6 \\ -19 x & + & 21 y & =45 \end{array}\right.