\[\boxed{\text{945\ (945).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[12x + 3 - 10x + 15 = 15x - 60\]
\[- 13x = - 78\]
\[x = 6\]
\[Ответ:x = 6.\]
\[9x - 15 - 20x + 8 = 12x + 108\]
\[- 23x = 115\]
\[x = - 5\]
\[Ответ:\ x = - 5.\]