greatest common factor of 45 51 63
\(45|3\\15|3\\.\ 5|5\\.\ 1|\\45=\fbox3\times3\times5\\\\51|3\\17|17\\.\ 1|\\51=\fbox3\times17\\\\63|3\\21|3\\.\ 7|7\\.\ 1|\\63=\fbox3\times3\times7\\\\GCF(45;\ 51;\ 63)=\fbox3\)