Answer:
first find the common factors of 18,26 and 72.
18: 1,2,3,6,9,18
26: 1,2,13,26
72: 1,2,3,4,6,8,12,18,24,36,72
next, find the common factors which can divide all numbers: 2
then find the highest factor which can divide all numbers. in this case, we only have one factor which is 2 and that shall be the H.C.F.
