\(Greatest\ common\ factor\ is\ the\ highest\ number\ by\ witch\ 54\ and\ 30\\and\ 78\ can\ be\ divided\\\\
54:2\\
27:3\\9:3\\3:3\\\\
30:2\\
15:3\\
5:5\\\\78:2\\39:3\\13:13
\\\\GCF=2*3=6\\\\Greatest\ common\ factor\ of\ 54\ and\ 30\ and\ 78\ is\ equal\ to\ 6.\)
